Wheel bearing apparatus and axle module

ABSTRACT

Provided are a low-cost wheel bearing device and axle module which are manufactured by small work man-hours and assemblyman-hours and at lower component replacement cost for maintenance and repairing. A recess-projection fitting structure is configured by providing projections extending in an axial direction on any one of an outer diameter surface of a shaft section of an outer joint member and an inner diameter surface of a hole of a hub wheel, press-fitting the projections in another of the outer diameter surface and the inner diameter surface along the axial direction, and forming recesses brought into close contact and fitted with respect to the projections by this press fitting in the another of the outer diameter surface and the inner diameter surface, the projections and the recesses being held in close contact with each other through intermediation of entire fitting contact regions. An outer member is fitted in a hole of a knuckle of a vehicle with a predetermined fit. Annular grooves are formed respectively in an outer peripheral surface of the outer member and an inner peripheral surface of the hole of the knuckle, and a snap ring is engaged with both the annular grooves. Consequently, the outer member is separable from the knuckle only by deformation or breakage of the snap ring caused by application of a drawing force larger than a drawing force acting in normal use.

TECHNICAL FIELD

The present invention relates to a wheel bearing device and an axlemodule for supporting wheels to freely rotate the wheels relative to avehicle body in a vehicle such as an automobile.

BACKGROUND ART

The wheel bearing device has evolved from a structure called firstgeneration in which a double row roller bearing is independently used tosecond generation in which a vehicle body attachment flange isintegrally provided in an outer member. Further, third generation inwhich one inner raceway surface of the double row roller bearing isintegrally formed with an outer periphery of a hub wheel integrallyincluding a wheel attachment flange has been developed. Further, fourthgeneration in which a constant-velocity universal joint is integratedwith the hub wheel and the other inner raceway surface of the double rowroller bearing is integrally formed with an outer periphery of an outerjoint member constituting the constant-velocity universal joint has beendeveloped.

For example, the wheel bearing device called third generation isdescribed in Patent Literature 1. The wheel bearing device called thirdgeneration includes, as illustrated in FIG. 45, a hub wheel 152including a flange 151 extending in an outer diameter direction, aconstant-velocity universal joint 154 including an outer joint member153 fixed to the hub wheel 152, and an outer member 155 disposed on anouter peripheral side of the hub wheel 152.

The constant-velocity universal joint 154 includes the outer jointmember 153, an inner joint member 158 disposed in a cup-like section 157of the outer joint member 153, balls 159 disposed between the innerjoint member 158 and the outer joint member 153, and a cage 160 thatretains the balls 159. Further, a spline section 161 is formed on aninner peripheral surface of a center hole of the inner joint member 158.An end spline section of a shaft (not shown) is inserted into the centerhole, and thus the spline section 161 on the inner joint member 158 sideand the spline section on the shaft side are engaged.

Further, the hub wheel 152 includes a cylindrical shaft section 163 andthe flange 151. A short-cylindrical pilot section 165, on which a wheeland a brake rotor (not shown) are mounted, is protrudingly provided onan outer end surface 164 (end surface on an outboard side) of the flange151. Note that, the pilot section 165 includes a large-diameter firstsection 165 a and a small-diameter second section 165 b. The brake rotoris externally fit in the first section 165 a and the wheel is externallyfit in the second section 165 b.

A small-diameter step section 166 is provided in an outer peripheralsurface at an end on the cup-like section 157 side of the shaft section163. An inner race 167 is fit in the small-diameter step section 166. Afirst inner raceway surface 168 is provided in the vicinity of a flangeon an outer peripheral surface of the shaft section 163 of the hub wheel152. A second inner raceway surface 169 is provided on an outerperipheral surface of the inner race 167. Further, a bolt inserting hole162 is provided in the flange 151 of the hub wheel 152. A hub bolt forfixing the wheel and the brake rotor to the flange 151 is inserted intothe bolt inserting hole 162.

In the outer member 155, outer raceway surfaces 170 and 171 in two rowsare provided on an inner periphery thereof and a flange (vehicle bodyattachment flange) 182 is provided on an outer periphery thereof. Thefirst outer raceway surface 170 of the outer member 155 and the firstinner raceway surface 168 of the hub wheel 152 are opposed to eachother. The second outer raceway surface 171 of the outer member 155 andthe raceway surface 169 of the inner race 167 are opposed to each other.Rolling elements 172 are interposed between the second outer racewaysurface 171 and the raceway surface 169. Further, the vehicle bodyattachment flange 182 is provided on the outer peripheral surface (outerdiameter surface) of the outer member 155, the flange 182 being attachedto a knuckle (not shown).

A shaft section 173 of the outer joint member 153 is inserted into theshaft section 163 of the hub wheel 152. In the shaft section 173, ascrew section 174 is formed at an end of a reverse cup-like sectionthereof. A spline section 175 is formed between the screw section 174and the cup-like section 157. Further, a spline section 176 is formed onan inner peripheral surface (inner diameter surface) of the shaftsection 163 of the hub wheel 152. When the shaft section 173 is insertedinto the shaft section 163 of the hub wheel 152, the spline section 175on the shaft section 173 side and the spline section 176 on the hubwheel 152 side are engaged.

A nut member 177 is screwed onto the screw section 174 of the shaftsection 173 projecting from the shaft section 163. Then, the hub wheel152 and the outer joint member 153 are connected. In this case, an innerend surface (rear surface) 178 of the nut member 177 and an outer endsurface 179 of the shaft section 163 come into contact with each otherand an end surface 180 on a shaft section side of the cup-like section157 and an outer end surface 181 of the inner race 167 come into contactwith each other. In other words, when the nut member 177 is tightened,the hub wheel 152 is nipped by the nut member 177 and the cup-likesection 157 through intermediation of the inner race 167.

PRIOR ART DOCUMENTS Citation List

Patent Literature 1: JP 2004-340311 A

SUMMARY OF INVENTION Technical Problems

Conventionally, as described above, the spline section 175 on the shaftsection 173 side and the spline section 176 on the hub wheel 152 sideare engaged. Therefore, because it is necessary to apply splinemachining to both spline sections on the shaft section 173 side and onthe hub wheel 152 side, cost increases. When the shaft section 173 ispress-fitted into the hub wheel 152, recesses and projections of thespline section 175 on the shaft section 173 side and the spline section176 on the hub wheel 152 side need to be aligned. In this case, if theshaft section 173 is press-fitted into the hub wheel 152 by aligningtooth surfaces thereof, recessed and projected teeth are likely to bedamaged (torn). Further, if the shaft section 173 is press-fitted intothe hub wheel 152 by aligning the spline sections to a large diameter ofthe recessed and projected teeth without aligning the tooth surfaces, abacklash in a circumferential direction tends to occur. If the backlashoccurs in the circumferential direction in this way, transferability ofrotation torque is low and abnormal noise tends to occur. Therefore,when the shaft section is press-fitted into the hub wheel by the splinefitting as in the prior art, it is difficult to remove damages to therecessed and projected teeth and the backlash in the circumferentialdirection at the same time.

Incidentally, even if adhesiveness of a male spline and a female splineis improved in the spline fitting to prevent the backlash in thecircumferential direction from occurring, if driving torque acts, it islikely that relative displacement occurs in the male spline and thefemale spline. If such relative displacement occurs, fretting wearoccurs. The splines are likely to cause abrasion because of dust of thewear. Consequently, it is likely that a backlash occurs in a splinefitting region or stable torque transmission cannot be performed.

Further, as described above, the outer member 155 is mounted to aknuckle on a vehicle body side in each wheel bearing device of thistype. In recent years, a cylindrical surface formed of an outer diametersurface of the outer member 155 is provided as a press-fitting surfacerather than providing the flange 182, and the press-fitting surface ispress-fitted in the hole of the knuckle. However, reliability of aslip-off preventing effect is low only with such press fitting.Therefore, a snap ring is used as slip-off preventing means.

When the snap ring is used, at the time of maintenance, repairing, andthe like, it is difficult to dismount the outer member from the knuckleand high drawing load is inevitably applied for disassembly. As aresult, because a snap ring groove of the knuckle is broken, the knucklealso needs to be replaced, which involves higher cost of maintenance andrepairing.

In view of the above-mentioned problem, a first object of the presentinvention is to provide a wheel bearing device in which a shaft sectionof an outer joint member of a constant-velocity universal joint isintegrated with a hub wheel through intermediation of arecess-projection fitting structure over a long period of time. A secondobject of the present invention is to provide a low-cost driving wheelbearing device and an axle module which are manufactured by small workman-hours and assembly man-hours and at lower component replacement costfor maintenance and repairing.

Solution to Problem

A first wheel bearing device according to the present invention includesa wheel bearing including: an outer member having double-row outerraceway surfaces formed on an inner periphery of the outer member; aninner member having double-row inner raceway surfaces formed on an outerperiphery of the inner member; and rolling elements arranged between thedouble-row outer raceway surfaces of the outer member and the double-rowinner raceway surfaces of the inner member, the inner member including ahub wheel having a wheel attachment flange protrudingly provided on anouter diameter surface of the hub wheel, the hub wheel and a shaftsection of an outer joint member of a constant-velocity universal jointbeing coupled to each other through intermediation of arecess-projection fitting structure, the shaft section being fitted andinserted in a hole of the hub wheel, in which: the recess-projectionfitting structure is configured by providing projections extending in anaxial direction on any one of an outer diameter surface of the shaftsection of the outer joint member and an inner diameter surface of thehole of the hub wheel, press-fitting the projections in another of theouter diameter surface and the inner diameter surface along the axialdirection, and forming recesses brought into close contact and fittedwith respect to the projections by this press fitting in the another ofthe outer diameter surface and the inner diameter surface, theprojections and the recesses being held in close contact with each otherthrough intermediation of entire fitting contact regions; and the outermember is separable in the following configuration from a knuckle onlyby deformation or breakage of a snap ring caused by application of adrawing force larger than a drawing force acting in normal use, theconfiguration being obtained by fitting the outer member in a hole ofthe knuckle of a vehicle with a predetermined fit, forming annulargrooves respectively in an outer peripheral surface of the outer memberand an inner peripheral surface of the hole of the knuckle, andpreventing the outer member from slipping off from the knuckle by thesnap ring engaged with both the annular grooves.

According to the wheel bearing device of the present invention, therecess-projection fitting structure is configured by press-fitting theprojections, which are provided on any one of the outer diameter surfaceof the stem shaft of the outer joint member and the inner diametersurface of the hole of the hub wheel and which extend in the axialdirection, in the another of the outer diameter surface and the innerdiameter surface along the axial direction, and by forming, with theprojections, the recesses brought into close contact and fitted withrespect to the projections in the another of the outer diameter surfaceand the inner diameter surface. That is, the shape of the projections istransferred to a recess formation surface on the opposite side. When theshape is transferred, because the projections bite into the recessformation surface on the opposite side, the hole is slightly expanded indiameter and allows movement in the axial direction of the projections.If the movement in the axial direction stops, the hole is reduced indiameter to return to the original diameter. Consequently, the entirerecess fitting regions of the projections come into close contact withthe recesses corresponding thereto. In this case, gaps may be inevitablyformed only in small parts of the fitting regions in a recess formationprocess by the projections in some cases.

In this way, the entire recess fitting regions of the projections areheld in close contact with the recesses corresponding thereto in therecess-projection fitting structure. Thus, in the fitting structure,gaps causing backlashes are not formed in the radial direction or thecircumferential direction.

As an example of the bearing, in the case of adopting a double-rowangular ball type, the bearing is constituted by an outer member havingouter raceways in two rows, an inner member having inner raceways in tworows, and rolling elements (balls, in this case) interposed between theouter raceways and the inner raceways. The inner member corresponding tothe bearing inner race includes a hub wheel and an inner race eachhaving an inner raceway in one row, and can be fixed by fitting theinner race in the hub wheel and caulking the end portion of the hubwheel. There may be adopted orbital forming as an example of variousknown machining methods. By caulking the end portion of the hub wheel,an interval between the inner raceways in two rows is narrowed andbearing preload is applied. The outer member corresponding to thebearing outer race is in a fitting relation with the hole of theknuckle.

The outer joint member includes the shaft section and a mouth sectionfor storing therein an inner joint member and torque transmissionelements, and a boot is mounted to an opening end portion of the outerjoint member. Generally, a maximum outer diameter of a boot band fortightening the boot from the outside is a maximum outer diameter of adrive shaft. Therefore, by setting an outer diameter of the outer memberto be larger than the maximum outer diameter, the drive shaft can betaken out as a whole from the hole of the knuckle to an outboard side.

The drive shaft is constituted by an outboard-side constant-velocityuniversal joint, a shaft, and an inboard-side constant-velocityuniversal joint, and has a function of transmitting torque from anengine to wheels. The inboard-side constant-velocity universal joint iscoupled to an output shaft of a transmission so as to allow torquetransmission and to be movable in the axial direction by a slide spline.The outboards-side constant-velocity universal joint transmits torquethrough intermediation of the hub wheel.

By setting a fitting relation between the outer member and the hole ofthe knuckle as a tight-fitting relation, it is possible to preventslip-off in the axial direction to some extent. However, excessivetightening margin cannot be set. Therefore, in order to realize, byperforming reliable slip-off prevention, a fail-safe and a measureagainst the case of application of unexpected high load, the snap ringis used in combination in the present invention. In addition, becausethe outer member is separable from the knuckle only by deformation orbreakage of the snap ring caused by application of the drawing forcelarger than the drawing force acting in normal use, the snap ring is notdeformed or broken with the drawing force acting in normal use.Therefore, the separation of the outer member from the knuckle isregulated. Further, when the drawing force larger than the drawing forceacting in normal use is applied, the snap ring is deformed or broken,and the outer member can be separated from the knuckle.

In this case, it is preferred to use a snap ring made of a materialsmaller in shearing stress than the knuckle and the outer member.Specifically, it is preferred that the shearing stress of the snap ringranges from 5 to 150 MPa. Consequently, it is possible to effectivelyprevent the knuckle or the outer member from being deformed or brokenearlier than the snap ring. There may be provided a thermoplasticsynthetic resin as an example of materials of such a snap ring.

An outer-diameter side ridge line section of the snap ring may bechamfered. The chamfering may be performed in a case where the snap ringhas a rectangular sectional shape. Alternatively, a snap ring having acircular sectional shape may be used. In other words, it is possible toadopt a snap ring made of a wire rod having a circular sectional shape.An outboard-side edge of the hole of the knuckle may be chamfered.

It is preferred that the outer member be fitted in the hole of theknuckle by pressfitting, and that at a time of this press fitting, afterbeing reduced in diameter by being guided to the inner peripheralsurface of the hole of the knuckle and then allowed to slide to theannular groove of the hole of the knuckle, the snap ring engaged withthe annular groove in the outer peripheral surface of the outer memberbe engaged with the annular groove of the hole of the knuckle by beingexpanded in diameter in a state of corresponding to the annular grooveof the hole of the knuckle. With this configuration, when the snap ringis inserted into the hole of the knuckle in a state of being mounted tothe outer peripheral surface of the outer member and reduced in diameterby elastic deformation, and then moved in the axial direction, the snapring is expanded in diameter by elasticity and expanded in the hole ofthe knuckle as soon as arriving at the position of the snap ring grooveof the hole of the knuckle. In this way, the snap ring is engaged withboth the snap ring grooves.

A second wheel bearing device according to the present inventionincludes a wheel bearing including: an outer member having double-rowouter raceway surfaces formed on an inner periphery of the outer member;an inner member having double-row inner raceway surfaces formed on anouter periphery of the inner member; and rolling elements arrangedbetween the double-row outer raceway surfaces of the outer member andthe double-row inner raceway surfaces of the inner member, the innermember including a hub wheel having a wheel attachment flangeprotrudingly provided on an outer diameter surface of the hub wheel, thehub wheel and a shaft section of an outer joint member of aconstant-velocity universal joint being separably coupled to each otherthrough intermediation of a recess-projection fitting structure, theshaft section being fitted and inserted in a hole of the hub wheel, inwhich: the recess-projection fitting structure is configured byproviding projections extending in an axial direction on any one of anouter diameter surface of the shaft section of the outer joint memberand an inner diameter surface of the hole of the hub wheel,press-fitting the projections in another of the outer diameter surfaceand the inner diameter surface along the axial direction, and formingrecesses brought into close contact and fitted with respect to theprojections by this press fitting in the another of the outer diametersurface and the inner diameter surface, the projections and the recessesbeing held in close contact with each other through intermediation ofentire fitting contact regions; and compressive residual stress isapplied to the projections by compressive-residual-stress applicationmeans.

Because the compressive residual stress is applied to the projections,improvement of the wear resistance of the projections is realized.Specifically, by applying compressive residual stress, residualaustenite can be transformed into martensite, and thus the wearresistance can be improved.

The compressive-residual-stress application means may include shotpeening. The shot peening means a cold working method of acceleratingand ejecting hard small balls called a shot material with a projectingdevice and the like and causing the small balls to collide against aworking subject material a thigh speed. Although a surface of theworking subject material is formed to be rough to some extent, a surfacelayer thereof is subjected to work hardening, and high compressiveresidual stress is applied thereto. Further, when a carburized materialis used as the working subject material, residual austenite istransformed into deformation induced martensite.

The projections of the recess-projection fitting structure are providedon the stem shaft of the outer joint member of the constant-velocityuniversal joint, at least hardness of axial end portions of theprojections is set to be higher than hardness of an inner diametersection of the hole of the hub wheel, and the stem shaft is press-fittedinto the hole of the hub wheel from an axial end portion side of theprojections. Thus, the recesses brought into close contact and fittedwith respect to the projections are formed in the inner diameter surfaceof the hole of the hub wheel by the projections, and therecess-projection fitting structure may be configured. Further, theprojections of the recess-projection fitting structure are provided onthe inner diameter surface of the hole of the hub wheel, at least thehardness of the axial end portions of the projections is set to behigher than hardness of an outer diameter section of the stem shaft ofthe outer joint member of the constant-velocity universal joint, and theprojections on a hub wheel side are press-fitted into the stem shaft ofthe outer joint member from the axial end portion side of theprojections. Thus, the recesses brought into close contact and fittedwith respect to the projections are formed in an outer diameter surfaceof the stem shaft of the outer joint member by the projections, and therecess-projection fitting structure may be configured.

It is preferred that hardness (Rockwell Hardness) of the projections beof from 50 HRC to 65 HRC, and hardness (Rockwell Hardness) of theopposite side on which the projections are press-fitted be of from 10HRC to 30 HRC. When the hardness of the projections ranges from 50 HRCto 65 HRC, hardness sufficient for being press-fitted in the oppositeside can be provided. Further, when the hardness on the opposite sideranges from 10 HRC to 30 HRC, the projections can be press-fitted.

It is preferred that the projections be hardened by heat hardeningtreatment, that is, by high-frequency heat treatment. The inductionhardening is a hardening method employing the principle of inserting asection necessary for hardening into a coil through which ahigh-frequency current flows, generating Joule heat with anelectromagnetic induction action, and heating a conductive substance.

It is preferred that a circumferential thickness of a projectingdirection intermediate region of each of the projections be set to besmaller than a circumferential dimension at a position corresponding tothe projecting direction intermediate region between the projectionsadjacent to each other in a circumferential direction. By setting thecircumferential thickness in this way, it is possible to set a sum ofcircumferential thicknesses of projecting direction intermediate regionsof the projections to be smaller than a sum of circumferentialthicknesses at positions corresponding to the projecting directionintermediate regions in projections on an opposite side that fit inamong the projections adjacent to one another in the circumferentialdirection.

It is preferred that the recess-projection fitting structure allowseparation by application of the drawing force in the axial direction.In this case, if the drawing force in the axial direction is applied tothe shaft section of the outer joint member, it is possible to removethe outer joint member from the hole of the hub wheel. After the shaftsection of the outer joint member is drawn out from the hole of the hubwheel, if the shaft section of the outer joint member is press-fittedinto the hole of the hub wheel again, it is possible to configure therecess-projection fitting structure in which the entire fitting contactregions of the projections and the recesses are held in close contactwith each other.

It is preferred that the inner diameter surface of the hub wheel beprovided with a wall section with which a distal end portion of theshaft section of the outer joint member of the constant-velocityuniversal joint comes into contact so that positioning of the shaftsection in the axial direction is performed. By providing the wallsection, bolt fixation is stabilized and a stable length can be securedas an axial length of the recess-projection fitting structure disposedalong the axial direction.

By providing the wall section, a stable length can be secured as theaxial length of the recess-projection fitting structure disposed alongthe axial direction.

A shaft section slip-off preventing structure may be provided betweenthe shaft section of the outer joint member and the inner diametersurface of the hub wheel. It is possible to prevent the outer jointmember of the constant-velocity universal joint from slipping off fromthe hub wheel in the axial direction by providing the shaft sectionslip-off preventing structure. At this time, it is preferred that theshaft section slip-off preventing structure be constituted by an endexpanded-diameter caulking section of the shaft section of the outerjoint member, the end expanded-diameter caulking section being engagedwith the inner diameter surface of the hub wheel and being unsubjectedto hardening treatment.

An axle module according to the present invention includes: anoutboard-side constant-velocity universal joint; an inboard-sideconstant-velocity universal joint; and a shaft connected to theoutboard-side constant-velocity universal joint on one end side of theshaft and connected to the inboard-side constant-velocity universaljoint on another end side of the shaft, in which the constant-velocityuniversal joint of the wheel bearing device is used as the outboard-sideconstant-velocity universal joint. In this case, it is preferred that amaximum outer diameter of each of the outboard-side constant-velocityuniversal joint and the inboard-side constant-velocity universal jointbe set to be smaller than an outer diameter of the outer member of thewheel bearing of the wheel bearing device.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the gaps causing backlashes are notformed in the radial direction or the circumferential direction in therecess-projection fitting structure. Therefore, the entire fittingregions contribute to rotation torque transmission, stable torquetransmission is possible, and abnormal noise is not generated. Inaddition, the recesses and the projections are held in close contactwith each other without gaps, and hence strength of the torquetransmitting regions is improved. Thus, weight reduction andcompactification of the wheel bearing device can be realized. Further,because the snap ring is not deformed or broken with the drawing forceacting in normal use, the separation of the outer member from theknuckle is regulated. Thus, this wheel bearing device is connected tothe knuckle in a stable state.

Under the state in which the wheel bearing device is mounted to theknuckle, the snap ring is deformed or broken by application of thedrawing force larger than the drawing force acting in normal use.Consequently, without damaging the annular groove of the knuckle, theannular groove of the outer member, and the like, the outer member, andby extension, the wheel bearing device can be separated as a whole fromthe knuckle.

By press-fitting the projections, which are provided on any one of theouter diameter surface of the stem shaft of the outer joint member andthe inner diameter surface of the hole of the hub wheel and which extendin the axial direction, in the another of the outer diameter surface andthe inner diameter surface along the axial direction, it is possible toform the recesses brought into close contact and fitted with respect tothe projections. Thus, the recess-projection fitting structure can besurely formed. In addition, it is unnecessary to form in advance aspline section and the like in the member in which the recesses areformed, and thus work man-hours can be reduced. As a result, thefollowing advantages can be obtained: excellent productivity;unnecessity of phasing of splines; realization of improvement ofassemblability as a result of reduction of assembly man-hours;prevention of damage to the tooth surfaces during press fitting; andmaintenance of a stable fitting state.

Further, by making the shearing stress of the snap ring smaller thanthose of the knuckle and outer member, a risk of damaging the knuckleand the outer member is eliminated at the time of dismounting the outermember from the knuckle for maintenance, repairing, and the like.Therefore, it is possible to minimize component replacement at the timeof maintenance, repairing, and the like, and hence possible to provide alow-cost wheel bearing device as a whole.

When the snap ring having a chamfered outer-diameter side ridge linesection or the snap ring having a circular sectional shape is used, itis possible to easily perform work of press-fitting the outer member inthe hole of the knuckle. In other words, by adopting a snap ring made ofa wire rod having a circular sectional shape, press-fitting work withrespect to the hole of the knuckle is easily performed.

The outboard side of the hole of the knuckle is a side constituting anouter side of a vehicle in a state in which the knuckle is attached tothe vehicle, and constitutes an inlet section at the time ofpress-fitting the outer member. Thus, when the outboard-side edge of thehole of the knuckle is chamfered, this chamfered section plays a role ofgradually reducing the snap ring in diameter so as to allow the snapring to be easily set into the snap ring groove of the outer member whenthe outer member is press-fitted in the knuckle. Therefore, the outermember can be smoothly inserted into the hole of the knuckle.

Further, when the snap ring is reduced in diameter by elasticdeformation, the snap ring is expanded in diameter by elasticity as soonas arriving at the position of the snap ring groove of the hole of theknuckle, and is engaged with both the snap ring grooves. In this way,mounting work of the snap ring can be more easily performed.

According to the second wheel bearing device of the present invention,because compressive residual stress is applied to the projections,improvement of the wear resistance of the projections is realized.Therefore, even when driving torque acts and relative displacementsupposedly occurs in the recess-projection fitting structure, it ispossible to suppress occurrence of fretting wear, to thereby preventabrasive wear in the recess-projection fitting structure. Consequently,a torque transmitting function can be stably exerted without backlashover a long period of time.

The compressive-residual-stress application means may include shotpeening, and compressive residual stress can be stably increased by thepeening. In addition, general-purpose shot peening can be used, and thuscost reduction can be realized.

Further, the projections of the recess-projection fitting structure areprovided on the stem shaft of the outer joint member of theconstant-velocity universal joint, the hardness of the axial endportions of the projections is set to be higher than the hardness of theinner diameter section of the hole of the hub wheel, and the stem shaftis press-fitted into the hole of the hub wheel from the axial endportionside of the projections. As a result, it is possible to increase thehardness on the stem shaft side and improve the rigidity of the stemshaft. Further, the projections of the recess-projection fittingstructure are provided on the inner diameter surface of the hole of thehub wheel, the hardness of the axial end portions of the projections isset to be higher than the hardness of the outer diameter section of thestem shaft of the outer joint member of the constant-velocity universaljoint, and the projections on the hub wheel side are press-fitted intothe stem shaft of the outer joint member from the axial end portion sidethereof. As a result, it is unnecessary to perform hardness treatment(heat treatment) on the stem shaft side. Therefore, the outer jointmember of the constant-velocity joint member is excellent inproductivity.

When the hardness of the projections ranges from 50 HRC to 65 HRC,hardness sufficient for being press-fitted in the opposite side can beprovided, and thus press-fitting properties can be improved. When thehardness on the opposite side ranges from 10 HRC to 30 HRC, it isunnecessary to perform hardening treatment on the opposite side, andpossible to realize improvement of productivity.

The projections can be hardened by heat hardening treatment, that is, byhigh-frequency heat treatment. Thus, the following advantages of thehigh-frequency heat treatment can be realized (local heating can beperformed and hardening condition can be easily adjusted; oxidation isreduced because heating can be performed in a short period of time;hardening distortion is reduced in comparison with other methods;surface hardness is high and excellent wear resistance can be obtained;selection of the depth of the hardened layer is relatively easy; andautomation is easily realized and assembly into a machine process linecan be realized). In particular, high compressive residual stress can beapplied by combining the shot peening with the high-frequency heattreatment, and thus improvement of fatigue strength can be expected.

By setting the circumferential thickness of the projecting directionintermediate region of each of the projections to be smaller than adimension at the position corresponding to the intermediate regionbetween the projections adjacent to each other in the circumferentialdirection, it is possible to increase the circumferential thickness ofthe projecting direction intermediate region of each of the projectionson the side in which the recesses are formed (projections among theformed recesses). Therefore, it is possible to increase a shearing areaof each of the projections on the opposite side (projections having lowhardness among the recesses because the recesses are formed) and securetorsion strength. Moreover, because a tooth thickness of the projectionson the high hardness side is small, it is possible to reducepress-fitting load and realize improvement of press-fitting properties.

Further, when the recess-projection fitting structure allows separationby application of the drawing force in the axial direction with respectto the shaft section of the outer joint member, the outer joint membercan be removed from the hole of the hub wheel, and after being removed,can be press-fitted therein again.

Therefore, it is possible to more easily perform maintenance, repairing,inspection, replacement work of the components of the wheel bearingdevice. In addition, it is possible to replace only the componentsnecessary to be replaced, and to save component replacement cost formaintenance and repairing. Therefore, a low-cost wheel bearing devicecan be provided.

When the positioning inner wall is provided and positioning is performedthereby, dimension accuracy of this wheel bearing device is stabilized,and it is possible to secure a stable length as an axial length of therecess-projection fitting structure disposed along the axial directionand realize improvement of torque transmission performance.

With the shaft section slip-off preventing structure, it is possible toeffectively prevent the shaft section of the outer joint member fromslipping off in the axial direction from the hole of the hub wheel.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the wheel bearing device. Further, adiameter expansion work can be more easily performed when the endexpanded-diameter caulking section is unsubjected to hardeningtreatment.

The axle module in which the wheel bearing device as described above isused can be manufactured by small work man-hours and assembly man-hours.When deficiencies leading to replacement of the wheel bearing deviceoccur, it is possible to separate this wheel bearing device from theknuckle, separate the wheel bearing and the constant-velocity universaljoints from each other, replace only the components necessary to bereplaced, and save component replacement cost for maintenance andrepairing. In particular, by setting the maximum outer diameters of theoutboard-side constant-velocity universal joint and the inboard-sideconstant-velocity universal joint to be smaller than the outer diameterof the outer member of the wheel bearing of the wheel bearing device,those constant-velocity universal joints can be easily caused to passwith respect to the knuckle. Therefore, assemblability of the axlemodule can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A vertical sectional view of an axle module according to a firstembodiment of the present invention.

FIG. 2 An enlarged sectional view of a wheel bearing device in the axlemodule of FIG. 1.

FIG. 3A An enlarged sectional view of a recess-projection fittingstructure of the wheel bearing device of FIG. 2.

FIG. 3B An enlarged view of the X section of FIG. 3A.

FIG. 4 A partially enlarged view of the wheel bearing device of FIG. 2.

FIG. 5 A vertical sectional view illustrating a state of the wheelbearing device of FIG. 2 prior to press fitting.

FIG. 6 An enlarged sectional view of a main part of therecess-projection fitting structure of the wheel bearing device of FIG.2.

FIG. 7A A sectional view of a seal member part of the wheel bearingdevice of FIG. 2, illustrating a case where an O-ring is used.

FIG. 7B A sectional view of the seal member part of the wheel bearingdevice of FIG. 2, illustrating a case where a gasket is used.

FIG. 8 A graph showing a relationship between press-fitting load and ahardness difference.

FIG. 9 A vertical sectional view illustrating a process of assemblingthe axle module of FIG. 1 into a vehicle.

FIG. 10 Another vertical sectional view illustrating the process ofassembling the axle module of FIG. 1 into a vehicle.

FIG. 11 A vertical sectional view illustrating a state in which the axlemodule of FIG. 1 is assembled into a vehicle.

FIG. 12A A front view of a snap ring having a rectangular sectionalshape.

FIG. 12B A sectional view of a snap ring having a rectangular sectionalshape.

FIG. 13A A front view of a snap ring having a circular sectional shape.

FIG. 13B A sectional view of a snap ring having a circular sectionalshape.

FIG. 14 A vertical sectional view of a wheel bearing device,illustrating an example in which a brake rotor including a pilot sectionis mounted to a hub wheel.

FIG. 15 A vertical sectional view of a wheel bearing device,illustrating a case where a pilot section is provided to a hub wheel.

FIG. 16 An enlarged sectional view of a wheel bearing device in an axlemodule according to a second embodiment of the present invention.

FIG. 17 A sectional view illustrating a method of assembling the wheelbearing device illustrated in FIG. 16.

FIG. 18 Another sectional view illustrating the method of assembling thewheel bearing device illustrated in FIG. 16.

FIG. 19 An enlarged sectional view of a wheel bearing device in an axlemodule according to a third embodiment of the present invention.

FIG. 20 A sectional view illustrating a method of assembling the wheelbearing device illustrated in FIG. 19.

FIG. 21 Another sectional view illustrating the method of assembling thewheel bearing device illustrated in FIG. 19.

FIG. 22A An endview of an outer collar-like locking section over theentire circumference, illustrating an end surface of a shaft section ofan outer race of the wheel bearing device of FIG. 19.

FIG. 22B An end view of outer collar-like locking sections arranged at apredetermined pitch along a circumferential direction, illustrating theend surface of the shaft section of the outer race of the wheel bearingdevice of FIG. 19.

FIG. 23 An enlarged sectional view of a wheel bearing device in an axlemodule according to a fourth embodiment of the present invention.

FIG. 24 An enlarged sectional view of a wheel bearing device in an axlemodule according to a fifth embodiment of the present invention.

FIG. 25 An enlarged sectional view of a wheel bearing device in an axlemodule according to a sixth embodiment of the present invention.

FIG. 26 An enlarged sectional view of a wheel bearing device in an axlemodule according to a seventh embodiment of the present invention.

FIG. 27 An enlarged sectional view of a main part of the wheel bearingdevice of FIG. 26.

FIG. 28 A vertical sectional view of an axle module according to aneighth embodiment of the present invention.

FIG. 29 An enlarged sectional view of the wheel bearing device of FIG.28.

FIG. 30 An enlarged vertical sectional view of a recess-projectionfitting structure of the wheel bearing device of FIG. 28.

FIG. 31A A sectional view taken along the line W-W of FIG. 31.

FIG. 31B An enlarged sectional view of a first modification of a shaftsection press-fitting guide structure.

FIG. 31C An enlarged sectional view of a second modification of a shaftsection press-fitting guide structure.

FIG. 32 An enlarged sectional view of a main part of the wheel bearingdevice of FIG. 28.

FIG. 33 An enlarged sectional view of the wheel bearing device of FIG.28 prior to assembly.

FIG. 34 A sectional view of an axle module in an assembled state.

FIG. 35 A sectional view of a method of mounting an axle module to aknuckle.

FIG. 36 A sectional view illustrating a method of separating the wheelbearing device.

FIG. 37 A sectional view illustrating a method of re-press-fitting

FIG. 38A A sectional view illustrating a method of re-press-fitting,specifically, a state immediately prior to press-fitting.

FIG. 38B A sectional view illustrating a middle of the press-fitting.

FIG. 38C A sectional view illustrating a press-fitting completion state.

FIG. 39A A sectional view of a third modification of a shaft sectionpress-fitting guide structure.

FIG. 39B A sectional view of a fourth modification of a shaft sectionpress-fitting guide structure.

FIG. 39C A sectional view of a fifth modification of a shaft sectionpress-fitting guide structure.

FIG. 40 A vertical sectional view illustrating a state in which an axlemodule according to a ninth embodiment of the present invention ismounted to the knuckle.

FIG. 41 A vertical sectional view of the axle module of FIG. 40.

FIG. 42 A vertical sectional view illustrating a method of mounting theaxle module of FIG. 40 to the knuckle.

FIG. 43A A sectional view of a first modification of therecess-projection fitting structure.

FIG. 43B A sectional view of a second modification of therecess-projection fitting structure.

FIG. 44A A horizontal sectional view of a third modification of therecess-projection fitting structure.

FIG. 44B An enlarged horizontal sectional view of a third modificationof the recess-projection fitting structure.

FIG. 45 A vertical sectional view of a conventional wheel bearingdevice.

DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates an example of an axle module. The axle module can beroughly classified as a wheel-bearing-device part and a drive-shaftpart. The wheel bearing device is obtained by unifying an outer jointmember of an outboard-side constant-velocity universal joint T1, a hubwheel 1, and a roller bearing 2. The drive shaft includes a shaft 10,and the outboard-side constant-velocity universal joint T1 and aninboard-side constant-velocity universal joint T2 mounted to respectiveboth ends thereof. As just described above, the wheel bearing device andthe drive shaft include (the outer joint member of) the outboard-sideconstant-velocity universal joint T1 as a common component.

Although a Rzeppa type constant-velocity universal joint is exemplifiedas the outboard-side constant-velocity universal joint T1, there may beadopted other fixed type constant-velocity universal joints such as anundercut free type one including linear sections formed in groovebottoms of ball grooves. The constant-velocity universal joint T1includes, as main members, a joint outer race 5 as the outer jointmember, an joint inner race 6 as an inner joint member, a plurality ofballs 7 as torque transmission elements, and a cage 8 for retaining theballs 7.

The joint outer race 5 is made of medium carbon steel such as S53C whichcontains 0.40 to 0.80 weight % of carbon, formed of a mouth section 11and a shaft section (stem section) 12, as illustrated in FIG. 5, a backsurface 11 a is formed in a boundary section therebetween. The mouthsection 11 is formed in a cup-like shape and therefore opens at its oneend, and provided with a plurality of axially extending ball grooves 14formed in its spherical inner surface (inner spherical surface) 13 atequal circumferential intervals. As indicated by cross hatching, on theshaft section 12 of the joint outer race 5, a predetermined hardenedlayer H in which surface hardness is set in a range of from 58 to 64 HRC(Rockwell Hardness C-Scale) is formed from the back surface 11 a to theshaft section. Note that, a distal end of the shaft section 12 is notsubjected to surface hardening treatment, and thus is in a raw state.

The joint inner race 6 is made of medium carbon steel such as S53C whichcontains 0.40 to 0.80 weight % of carbon, and includes a spline hole 6 aat its axis section in which spline fitting is effected with respect toa spline shaft 10 a at an end of the shaft 10, to thereby be coupled tothe shaft 10 so that torque can be transmitted. The shaft 10 isprevented from being slipped off from the joint inner race 6 by a snapring 9 attached to the end portion of the shaft 10. The joint inner race6 has a spherical outer surface (outer spherical surface) 15, and has aplurality of axially extending ball grooves 16 formed at equalcircumferential intervals.

The ball grooves 14 of the outer race 5 and the ball grooves 16 of thejoint inner race 6 are paired with each other, and one ball 7 isincorporated into a ball track formed by each pair of ball grooves 14,16 so as to be capable of rolling. The balls 7 are interposed betweenthe ball grooves 14 of the joint outer race 5 and the ball grooves 16 ofthe joint inner race 6 to transmit torque. All the balls 7 are retainedin the same plane by the cage 8. The cage 8 is interposed between thejoint outer race 5 and the joint inner race 6 in a spherical-surfacecontact state. Specifically, the cage 8 comes into contact with theinner spherical surface 13 of the joint outer race 5 throughintermediation of the spherical outer surface thereof and comes intocontact with the outer spherical surface 15 of the joint inner race 6through intermediation of the spherical inner surface thereof.

In order to prevent leakage of lubricant filling the inside and toprevent intrusion of foreign matters from the outside, the openingportion of the mouth section 11 is covered with a boot 60. The boot 60is formed of a large diameter section 60 a, a small diameter section 60b, and a bellows section 60 c for connecting the large diameter section60 a and the small diameter section 60 b to each other. The largediameter section 60 a is mounted to the opening portion of the mouthsection 11 and fastened by a boot band 61. The small diameter section 60b is mounted to a boot mounting section 10 b and fastened by a boot band62.

Although a tripod type constant-velocity universal joint is exemplifiedas the inboard-side constant-velocity universal joint T2, there may beadopted other plunging type constant-velocity universal joints such as adouble-offset type one. The constant-velocity universal joint T2includes, as main components, a joint outer race 131 as an outer jointmember, a tripod 132 as an inner joint member, and rollers 133 as torquetransmission elements.

The joint outer race 131 is made of medium carbon steel such as S53Cwhich contains 0.40 to 0.80 weight % of carbon, formed of the mouthsection 131 a and a stem section 131 b, and allowed to be connected toan output shaft of a differential through intermediation of the stemsection 131 b so that torque can be transmitted. The mouth section 131 ais formed in a cup-like shape and therefore opens at its one end, andprovided with axially extending track grooves 136 formed atcircumferentially trisected positions on an inner periphery thereof.Thus, the mouth section 131 a exhibits a bell-like shape in horizontalcross-section. On outer peripheries of the track grooves 136 and stemsection 131 b, a predetermined hardened layer in which surface hardnessis set in a range of from 58 to 64 HRC is formed by induction hardening.

The tripod 132 is formed of bosses 138 and leg shafts 139, and coupledto an end spline 10 c of the shaft 10 through intermediation of a splinehole 138 a of each of the bosses 138 so that torque can be transmitted.The leg shafts 139 radially project from circumferentially trisectedpositions of the bosses 138. The rollers 133 are rotatably supported bythe leg shafts 139, respectively.

Also in this section, the opening portion of the joint outer race 131 iscovered with a boot 140 mounted thereto. With this configuration, it ispossible to prevent leakage of lubricant filling the inside and toprevent intrusion of foreign matters from the outside. The boot 140 isformed of a large diameter section 140 a, a small diameter section 140b, and a bellows section 140 c between the large diameter section 140 aand the diameter section 140 b. The large diameter section 140 a ismounted to an opening end portion of the mouth section 131 a andfastened by a boot band 141, and the small diameter section 140 b ismounted to a boot mounting section 10 d of the shaft 10 and fastened bythe boot band 141.

Next, the hub wheel 1 is made of medium carbon steel such as S53C whichcontains 0.40 to 0.80 weight % of carbon, and has, as is apparent fromFIGS. 2 and 5, a cylindrical section 20 and a flange 21 provided at anoutboard-side end portion of the cylindrical section 20. The flange 21of the hub wheel 1 is provided with a bolt inserting hole 32, and awheel and a brake rotor are fixed to the flange 21 by a hub bolt 33embedded in the bolt inserting hole 32. A small diameter section 23 isformed at an inboard-side end portion of the cylindrical section 20, andan inner race 24 is fitted thereto. Then, an end portion of the smalldiameter section 23 is caulked to an outer diameter side, and a caulkingsection 31 thus formed is abutted to an end surface of the inner race24. In this way, the inner race 24 is fixed to the hub wheel 1, andsimultaneously, preload is applied to the bearing 2.

The cylindrical section 20 has a hole 22 (FIG. 5) passing through itsaxis section. The hole 22 includes, around a fitting hole 22 a at anaxial intermediate section as a center, a tapered hole 22 b positionedon an outboard side and a large diameter section 22 c on aninboard-side. In the fitting hole 22 a, the shaft section 12 of thejoint outer race 5 of the constant-velocity universal joint T1 and thehub wheel 1 are coupled to each other through intermediation of arecess-projection fitting structure M described later. Further, thefitting hole 22 a and the large diameter section 22 c are connected toeach other through intermediation of a tapered section 22 d. The taperedsection 22 d is reduced in diameter in a press-fitting direction at thetime of coupling the hub wheel 1 and the shaft section 12 of the jointouter race 5 to each other. An angle θ1 (FIG. 5) of the tapered section22 d is set to 15° to 75°, for example.

As indicated by cross hatching of FIG. 5, on the hub wheel 1, apredetermined hardened layer H1 in which surface hardness is set in arange of from 58 to 64 HRC is formed by induction hardening over a rangefrom a seal land section with which a seal lip of an outboard-side sealmember S1 comes into sliding-contact to a part of the small diametersection 23, the range including an inner raceway surface 28. With thisconfiguration, wear resistance of the seal land section is improved, andin addition, the strength of the hub wheel 1 itself with respect tomoment load and the like is increased, and thus durability thereof isimproved. Further, it is preferred that a section subjected to plasticdeformation so as to be formed as a caulking section 31 remain anunhardened section having hardness the same as that of a surface of araw material after forging.

The roller bearing 2 includes, as main components, an outer member 25corresponding to a bearing outer race, an inner member 39 correspondingto a bearing inner race, and rolling elements 30. The outer member 25 ismade of high-carbon chrome bearing steel such as SUJ2, and has an outerperipheral surface formed in a cylindrical shape and double-row outerraceway surfaces (outer raceway) 26 and 27 formed on an inner peripherythereof. The inner member 39 in this case is formed of the hub wheel 1and the inner race 24. Specifically, the first inner raceway surface(inner raceway) 28 is formed on a flange 21 side of the cylindricalsection 20 of the hub wheel 1, and a second inner raceway surface (innerraceway) 29 is formed on an outer periphery of the inner race 24 fittedto the small diameter section 23 of the hub wheel 1. A hardened layer inwhich surface hardness is set in a range of from 58 to 64 HRC is formedon the raceway surface 28 by induction hardening. The inner race 24 ismade of high-carbon chrome bearing steel such as SUJ2, and a hardenedlayer in which surface hardness is set in a range of from 58 to 64 HRCis formed on the raceway surface 29 by immersion quenching. In thiscontext, the first outer raceway surface 26 and the first inner racewaysurface 28 are opposed to each other, the second outer raceway surface27 and the second inner raceway surface 29 are opposed to each other,and the rolling elements 30 are interposed therebetween. The rollingelements 30 in each of the rows are retained by a cage at predeterminedintervals.

In order to prevent leakage of lubricant filling the inside and toprevent intrusion of foreign matters from the outside, the seal memberS1 and a seal member S2 are mounted around both-end opening portions ofthe outer member 25. Note that, as described later, the outer member 25is allowed to be fitted to an inner peripheral surface 34 a of a hole ofa knuckle 34 (refer to FIG. 9) extending from a vehicle suspensionsystem.

The hub wheel 1 and the shaft section 12 of the joint outer race 5 ofthe constant-velocity universal joint T1 are coupled to each otherthrough intermediation of the recess-projection fitting structure M. Asillustrated in FIG. 3A, the recess-projection fitting structure M isformed, for example, of axially extending projections 35 provided to anend portion of the shaft section 12, and recesses 36 formed in the innerdiameter surface of the hole 22 of the hub wheel 1 (inner diametersurface 37 of shaft section fitting hole 22 a in this case). The entireregions of the fitting contact regions 38 of the projections 35 and therecesses 36 fit in the projections 35 are held in close contact.Specifically, a plurality of the projections 35 are arranged at apredetermined circumferential pitch on the outer peripheral surface ofthe opposite mouth section side of the shaft section 12, and a pluralityof the recesses 36 fitting in the projections 35 are formedcircumferentially in the inner diameter surface 37 of the fitting hole22 a of the hole 22 of the hub wheel 1. That is, over the entirecircumference, the projections 35 and the recesses 36 fitting theretoare tightly fitted in each other.

In this case, each of the projections 35 is formed in a triangular shape(ridge shape) having a vertex of a projected circular shape incross-section. Recess fitting regions of the projections 35 are ranges Aillustrated in FIG. 3B, specifically, ranges from halfway sections ofthe ridges in cross-section to the tops of the ridges. Further, a gap 40is each formed further on an inner diameter side than the inner diametersurface 37 of the hub wheel 1 between the projections 35 adjacent toeach other in the circumferential direction.

As described above, bearing preload is applied by caulking the endportion on the inboard side of the hub wheel 1 and abutting the caulkingsection 31 to the end surface of the inner race 24. Thus, it isunnecessary to abut the back surface 11 a of the mouth section 11 of thejoint outer race 5 to the inner race 24, and possible to configure anon-contact structure in which the mouth section 11 is not brought intocontact with an end portion (caulking section 31 in this case) of thehub wheel 1. Thus, as illustrated in FIG. 2, a gap 98 exists between thecaulking section 31 of the hub wheel 1 and the back surface 11 a of themouth section 11. Note that, without problems of abnormal noise, it ispossible to configure a structure in which the mouth section 11 and thecaulking section 31 are held in contact with each other.

Foreign-matter intrusion preventing means W for the recess-projectionfitting structure M are respectively provided further on the inboardside (corresponding to an inner side of the vehicle in a state in whichthe recess-projection fitting structure M is mounted to the vehicle)than the recess-projection fitting structure M and further on theoutboard side (corresponding to an outer side of the vehicle in a statein which the recess-projection fitting structure M is mounted to thevehicle) than the recess-projection fitting structure M. Specifically,as enlargedly illustrated in FIGS. 7A and 7B, foreign-matter intrusionpreventing means W1 on the inboard side (FIG. 2) is formed of a sealmember 99 arranged in the gap 98 between the caulking section 31 of thehub wheel 1 and the back surface 11 a of the mouth section 11. In thiscase, the gap 98 includes a radial section between the caulking section31 of the hub wheel 1 and the back surface 11 a of the mouth section 11,and an axial section between the large diameter section 22 c of and theshaft section 12. The seal member 99 is arranged near a corner at whichthe radial section and the axial section of the gap 98 border eachother. Note that, the seal member 99 may be something like an O-ringillustrated in FIG. 7A, or may be something like a gasket illustrated inFIG. 7B.

As illustrated in FIG. 2 and FIG. 4, the outboard side foreign-matterintrusion preventing means W2 can be formed of a seal material (notshown) interposed between an end expanded-diameter caulking section 65serving as an engagement section and the inner diameter surface of thetapered hole 22 b. In this case, a seal material is applied to the endexpanded-diameter caulking section 65. That is, there is applied a sealmaterial (seal agent) selected from among various resins curable afterthe application and capable of exerting sealing property between the endexpanded-diameter caulking section 65 and the inner diameter surface ofthe tapered hole 22 b. Note that, as the seal material, there isselected one that does not deteriorate in the atmosphere in which thewheel bearing device is used.

It is also possible to interpose a seal material in the fitting contactregions 38 between the projections 35 and the recesses 36, and betweengaps 40, to thereby form a foreign-matter intrusion preventing means W(W3). In this case, there is applied to the surfaces of the projections35 a seal material (seal agent) selected from among various resinscurable after the application and capable of exerting sealing propertyin the fitting contact regions 38 and between the gaps 40.

A shaft section slip-off preventing structure M1 is provided between theend of the shaft section 12 of the joint outer race 5 and the innerdiameter surface 37 of the hub wheel 1. This shaft section slip-offpreventing structure M1 includes the end expanded-diameter caulkingsection (tapered locking piece) 65 that extends from the end of theshaft section 12 of the joint outer race 5 to the outboard side andlocks to a tapered hole 22 b. In other words, the tapered locking piece65 includes a ring-like member that is expanded in diameter from theinboard side to the outboard side. At least a part of an outerperipheral surface 65 a thereof comes into press-contact or contact withthe tapered hole 22 b.

When the wheel bearing device is assembled, as described later, therecesses 36 are formed by the projections 35 by press-fitting the shaftsection 12 of the joint outer race 5 into the hub wheel 1. At this time,when the shaft section 12 is press-fitted into the hub wheel 1, amaterial is extruded from the recesses 36 formed by the projections 35and an extruded portion 45 (refer to FIG. 4) is formed. The extrudedportion 45 is equivalent to a volume of the material of the recesses 36in which recess fitting regions of the projections 35 are fitted in. Theextruded portion 45 includes the material extruded from the recesses 36to be formed, the material cut for forming the recesses 36, or thematerial extruded and cut. Therefore, a pocket section (storage section)100 for storing the extruded portion 45 is provided to the shaft section12.

Here, the pocket section (storage section) 100 is formed by providing acircumferential groove 101 at a shaft edge of a spline of the shaftsection 12. The tapered locking piece (end expanded-diameter caulkingsection) 65 configuring the above-mentioned shaft section slip-offpreventing structure M1 is positioned further on an opposite spline sidethan the circumferential groove 101.

Next, a manufacturing method of fitting the recess-projection fittingstructure M is described. In this case, as illustrated in FIG. 5,surface hardening treatment is applied to an outer diameter section ofthe shaft section 12. The spline 41 including projections 41 a andrecesses 41 b extending along the axial direction is formed in thehardened layer H. Therefore, the projections 41 a of the spline 41 arehardened and change to the projections 35 of the recess-projectionfitting structure M. Note that, a range of the hardened layer H here is,as indicated by a cross hatching, from an outer edge of the spline 41 toa part of the back surface 11 a of the joint outer race 5. Here, as thesurface hardening treatment, various kinds of heat treatments such asinduction hardening, and carburizing and quenching can be adopted. Theinduction hardening is a hardening method applying the principle ofinserting a section necessary for hardening into a coil through which ahigh-frequency current flows, generating Joule heat with anelectromagnetic induction action, and heating a conductive substance.The carburizing and quenching is a method of causing carbon tointrude/spread from the surface of a low carbon material and performinghardening after that. A module of teeth of the spline 41 of the shaftsection 12 is set to be equal to or smaller than 0.5. The module is avalue obtained by dividing a pitch circle diameter with the number ofteeth.

Further, a hardened layer H1 by the induction hardening is formed on theouter diameter side of the hub wheel 1, and the inner diameter side ofthe hub wheel is left in an unhardened state. A range of the hardenedlayer H1 in this case is, as indicated by cross hatching, from a basesection of the flange 21 to the vicinity of the caulking section of thesmall diameter section 23 in which the inner race 24 fits. If theinduction hardening is performed, the surface can be hard and hardnessof a material in the inside can be kept as it is. Therefore, the innerdiameter side of the hub wheel 1 can be maintained in the unhardenedstate. A hardness difference between the hardened layer H of the shaftsection 12 of the joint outer race 5 and the unhardened section of thehub wheel 1 is set to be equal to or larger than 20 points in HRC. Asspecific examples, the hardness of the hardened layer H is set to about50 HRC to 65 HRC and the hardness of the unhardened section is set toabout 10 HRC to 30 HRC.

Compressive residual stress is applied to the projections 35 subjectedto heat hardening treatment in this way by compressive-residual-stressapplication means. The compressive-residual-stress application means mayinclude shot peening. The shot peening means a cold working method ofaccelerating and ejecting hard small balls called a shot material with aprojecting device and the like and causing the small balls to collideagainst a working subject material at high speed. Although a surface ofthe working subject material, which is subjected to shot peening, isformed to be rough to some extent, a surface layer thereof is subjectedto work hardening, and high compressive residual stress is appliedthereto. Further, residual austenite of the working subject material istransformed into deformation induced martensite.

In this case, a projecting direction intermediate region of each of theprojections 35 corresponds to a position of a recess forming surfacebefore recess formation (in this case, inner diameter surface 37 of hole22 of hub wheel 1). That is, as illustrated in FIG. 5, an inner diameterdimension D of the inner diameter surface 37 of the hole 22 is set to besmaller than a maximum outer diameter of the projections 35, i.e., amaximum outer diameter dimension (diameter of circumscribed circle) D1of a circle connecting vertexes of the projections 35 as the projections41 a of the spline 41, and is set to be larger than an outer diameterdimension of a shaft section outer diameter surface among theprojections, i.e., a diameter dimension D2 of a circle connectingbottoms of the recesses 41 b of the spline 41. In other words, thedimensions are set in a relation of D2<D<D1.

The structure of the spline and the processing method therefor arewell-known (refer to JIS B 0006: 1993). In other words, the spline canbe formed by various machining methods such as rolling, cutting,pressing, and drawing. Further, as the surface hardening treatment,various kinds of heat treatments such as induction hardening, andcarburizing and quenching can be adopted.

A short cylindrical section 66 for forming the tapered locking piece 65(FIGS. 2 and 4) is projected from an outer circumferential edge of anend surface of the shaft section 12 in the axial direction. An outerdiameter D4 of the short cylindrical section 66 is set to be smallerthan an inner diameter dimension D of a fitting hole 22 a of the hole22. Consequently, this short cylindrical section 66 performs aligningwork when the shaft section 12 is press-fitted into the hole 22 of thehub wheel 1 as described later.

As illustrated in FIG. 5, the shaft section 12 of the joint outer race 5is inserted (press-fitted) into the hub wheel 1 under a state in whichthe axis of the hub wheel 1 and the axis of the joint outer race 5 arealigned. Note that, the seal member 99 (refer to FIG. 2) is fitted inthe base section of the shaft section 12 of the joint outer race 5(mouth section side) in advance. In this case, because the taperedsection 22 d that is reduced in diameter in a press-fitting direction isformed in the hole 22 of the hub wheel 1, this tapered section 22 dexerts a guiding effect at the start of press fitting. Further, theinner diameter dimension D of the inner diameter surface 37 of the hole22, the outer diameter dimension D1 of the projections 35, and thediameter dimension D2 of the recesses of the spline 41 are in therelation described above. Moreover, the hardness of the projections 35is larger than the hardness of the inner diameter surface 37 of the hole22 by 20 points or more. Therefore, if the shaft section 12 ispress-fitted into the hole 22 of the hub wheel 1, the projections 35bite in the inner diameter surface 37 of the fitting hole 22 a. Theprojections 35 form the recesses 36, in which the projections 35 fit,along the axial direction.

By the press fitting, as illustrated in FIG. 3A, the entire fittingcontact regions 38 of the projections 35 at the end of the shaft section12 and the recesses 36 fitting therein are held in close contact witheach other. In other words, a shape of the projections 35 is transferredonto a recess formation surface on the opposite side (in this case,inner diameter surface 37 of fitting hole 22 a). Because the projections35 bite in the inner diameter surface 37 of the fitting hole 22 a, thefitting hole 22 a is slightly expanded in diameter and allows movementin the axial direction of the projections 35. If the movement in theaxial direction stops, the fitting hole 22 a is reduced in diameter toreturn to the original diameter. In other words, the hub wheel 1 iselastically deformed in the radial direction when the projections arepress-fitted, and preload equivalent to the elastic deformation isapplied to a tooth surface of the projections 35 (surface of the recessfitting region). Therefore, it is possible to surely form therecess-projection fitting structure M in which the entire recess fittingregions of the projections 35 are held in close contact with therecesses 36 corresponding thereto. In this way, the entire regions ofthe recess fitting region of the projections 35 are held in closecontact with the recesses 36 corresponding thereto. However, gaps may beinevitably formed only in a small part of the fitting region in a recessformation process by the projections in some cases.

Further, the seal member 99 is mounted to the base section of the shaftsection 12 of the joint outer race 5 (mouth section side). Therefore,the gap 98 between the caulking section 31 of the hub wheel 1 and theback surface 11 a of the mouth section 11 is closed by the seal member99 and therefore is hermetically-sealed in a press fitting completionstate.

When the shaft section 12 of the joint outer race 5 is press-fitted inthe hole 22 of the hub wheel 1, a step surface G is provided on theouter diameter surface of the mouth section 11 of the joint outer race 5as illustrated in FIG. 2 and the like. A press-fitting jig K only has tobe engaged with this step surface G to apply press-fitting load (axialload) from this press-fitting jig K to the step surface G. Note that,the step surface G may be provided over the entire circumferentialdirection or at a predetermined pitch in a circumferential direction.Therefore, the press-fitting jig K to be used only has to be capable ofbearing axial load corresponding to those step surfaces G.

Although the recess-projection fitting structure M is formed in thisway, it is desired that the axial position of the recess-projectionfitting structure M be positions avoiding the positions right below theraceway surfaces 26, 27, 28, and 29 of the roller bearing 2. Thepositions avoiding the positions right below the raceway surfaces 26,27, 28, and 29 are positions not corresponding to ball contactingpositions of the raceway surfaces 26, 27, 28, and 29 in the radialdirection.

As is understood from FIG. 5, the short cylindrical section 66 projectsfrom the fitting hole 22 a to a tapered hole 22 b side under a state inwhich the shaft section 12 of the joint outer race 5 and the hub wheel 1are integrally formed through intermediation of the recess-projectionfitting structure M. In this context, as illustrated by the imaginarylines of FIG. 2, this short cylindrical section 66 is expanded indiameter, that is, plastically deformed to the outer side in the radialdirection by the jig 67. The jig 67 includes a columnar main bodysection 68 and a truncated cone section 69 continuously connected to adistal end of the main body section 68. In the truncated cone section69, a tilt angle of a tilting surface 69 a thereof is set to besubstantially the same as a tilt angle of the tapered hole 22 b, and anouter diameter of a distal end of the truncated cone section 69 is setto a dimension the same as or slightly smaller than the inner diameterof the short cylindrical section 66.

Then, load in the arrow a direction is applied to the jig 67 and thetruncated cone section 69 of the jig 67 is fitted in the shortcylindrical section 66, and thus a force in the arrow β direction forexpanding a diameter of the short cylindrical section 66 is applied. Asa result, by the truncated cone section 69 of the jig 67, at least apart of the short cylindrical section 66 is pressed to the innerdiameter surface side of the tapered hole 22 b and is held inpress-contact or contact with the inner diameter surface of the taperedhole 22 b through intermediation of the seal material constituting theforeign-matter intrusion preventing means W2. Therefore, the shaftsection slip-off preventing structure M1 can be configured. Note that,when the load in the arrow a direction is applied to the jig 67, it isnecessary to fix this wheel bearing device so as not to move in thearrow a direction. However, a part of the hub wheel 1, theconstant-velocity universal joint T1, and the like only has to bereceived by a fixed member. An inner diameter surface of the shortcylindrical section 66 can be formed by forging when the inner diametersurface is expanded in diameter to an axial end side, that is, formed ina tapered shape, which leads to cost reduction.

A cutout may be formed in the short cylindrical section 66 in order toreduce the load in the arrow a direction of the jig 67. Further, aconical surface of the truncated cone section 69 of the jig 67 may bearranged in the entire circumferential direction or partially in thecircumferential direction. The diameter of the short cylindrical section66 is more easily expanded when the cutout is formed on the shortcylindrical section 66. When the conical surface of the truncated conesection 69 of the jig 67 is partially arranged in the circumferentialdirection, a region where the short cylindrical section 66 is expandedin diameter is a part on the circumference. Therefore, it is possible toreduce push-in load of the jig 67.

In the recess-projection fitting structure M, as illustrated in FIG. 6,when a diameter difference (D1-D) between the outer diameter dimensionD1 of the shaft section 12 and the inner diameter dimension D of thefitting hole 22 a of the hole 22 of the hub wheel 1 is represented asΔd, the height of the projections 35 provided on the outer diametersurface of the shaft section 12 is represented as h, and a ratio of thediameter difference and the height is represented as Δd/2 h, a relationamong the diameter difference, the height, and the ratio is set to be0.3<Δd/2 h<0.86. Consequently, the projecting direction intermediateregions (height direction intermediate regions) of the projections 35are surely arranged on the recess formation surface before recessformation. Therefore, the projections 35 bite in the recess formationsurface during press fitting and the recesses 36 can be surely formed.

Assembly of the axle module assembled as illustrated in FIG. 1 withrespect to a vehicle is completed by fitting, as illustrated in FIG. 11,the outer member 25 of the roller bearing 2 in the hole of the knuckle34. Thus, a predetermined fit is set between a cylindrical outerperipheral surface 25 a of the outer member 25 and the cylindrical innerperipheral surface 34 a of the hole of the knuckle 34. Then, a snap ring130 is interposed between the outer peripheral surface 25 a of the outermember 25 and the inner peripheral surface 34 a of the hole of theknuckle 34. By using the snap ring 130, a slip-off preventing effect ofthe outer member 25 with respect to the knuckle 34 is improved. That is,an annular groove 129 (FIG. 2) is formed in the outer peripheral surface25 a of the outer member 25, and an annular groove 128 (refer to FIG. 9)is formed similarly in the inner peripheral surface 34 a of the hole ofthe knuckle 34. Then, the snap ring 130 is engaged with both the annulargroove 129 of the outer member 25 and the annular groove of the knuckle34. That is, an inner diameter side of the snap ring 130 is engaged withthe annular groove 129 of the outer member 25, and an outer diameterside of the snap ring 130 is engaged with the annular groove 128 of theknuckle 34.

As illustrated in FIG. 1, an outer diameter D11 of the outer member 25is set to be larger than a maximum outer diameter dimension D12 of theconstant-velocity universal joint T1. The maximum outer diameterdimension D12 of the constant-velocity universal joint T1 means amaximum outer diameter dimension of this constant-velocity universaljoint T1 in a state of including auxiliaries such as the boot 60 and theboot band 61. Further, a maximum outer diameter dimension D13 of theinboard-side constant-velocity universal joint T2 is set to be smallerthan the outer diameter D11 of the outer member 25. Similarly to thecase of the outboard-side constant-velocity universal joint T1, themaximum outer diameter dimension D13 of the inboard-sideconstant-velocity universal joint T2 means a maximum outer diameterdimension of the inboard-side constant-velocity universal joint T2 in astate of including auxiliaries such as the boot 140 and the boot band141.

As illustrated in FIGS. 9 and 10, the assembly of the axle module withrespect to a vehicle is performed as follows: this axle module is letinto the knuckle 34 from an inboard-side constant-velocity universaljoint T2 side; the axle module is then caused to pass the outboard-sideconstant-velocity universal joint T1; and lastly, the outer member 25 ofthe driving wheel bearing device is press-fitted into the innerperipheral surface 34 a of the hole of the knuckle 34. In this case, themaximum outer diameter dimension D12 of each of the constant-velocityuniversal joints T1 and T2 is smaller than the outer diameter D11 of theouter member 25, and by extension, than an inner diameter D14 of theknuckle 34. Thus, the constant-velocity universal joints T1 and T2 areallowed to easily pass with respect to the knuckle 34, and thus assemblyworkability of the axle module can be improved. Note that, a chamferedsection 90 is provided on an outboard-side edge of the inner diametersurface 34 a of the knuckle 34.

In this case, it is preferred to set to regulate, with a tighteningmargin between the outer peripheral surface (knuckle press-fittingsurface) 25 a and the inner diameter surface 34 a, relative shift in anaxial direction and a circumferential direction of the knuckle 34 andthe outer member 25. For example, when fitting surface pressure×fittingarea between the outer member 25 and the knuckle 34 is fitting load, avalue obtained by dividing this fitting load with equivalent radial loadof this roller bearing is set as a creep occurrence limit coefficient. Adesign specification for the outer member 25, i.e., a fitting marginbetween the outer member 25 and the knuckle 34 is set by taking intoaccount this creep occurrence limit coefficient in advance. In addition,the outer diameter D11 of the outer member 25 (refer to FIG. 11 and thelike) and the inner diameter D14 of the knuckle 34 (refer to FIG. 9 andthe like) are set.

Therefore, it is possible to prevent slip-off in the axial direction andcreep in the circumferential direction of the outer member 25 with thetightening margin between the outer peripheral surface (knucklepress-fitting surface) 25 a of the outer member 25 and the knuckle innerdiameter surface 34 a of the knuckle 34. The creep means that thebearing slightly moves in the circumferential direction because ofinsufficiency of the fitting margin, machining accuracy failure of thefitting surface, or the like and the fitting surface changes to a mirrorsurface and, in some case, the fitting surface involves score andseizure, or adhesion occurs. As illustrated in FIG. 11, under a state inwhich the outer member 25 is press-fitted in the knuckle 34, the snapring 130 is engaged with the annular groove 129 of the outer peripheralsurface 25 a of the outer member 25 and the annular groove 128 of theinner peripheral surface 34 a of the knuckle 34.

FIGS. 12 and 13 each illustrate the snap ring 130. The snap ring 130illustrated in each of the figures is formed of a ring member having adeficient section 130 a in a part thereof. FIGS. 12A and 12B illustratean example of a snap ring having a rectangular sectional shape, andFIGS. 13A and 13B illustrate an example of a snap ring having a circularsectional shape. Therefore, the snap ring 130 is reduced in diameterfrom a free state each illustrated in FIGS. 12A and 13A by being appliedwith a diameter reducing force in an inner diameter direction, andreturns to the free state each illustrated in FIGS. 12A and 13B bycancelling application of the diameter reducing force.

In the case of the snap ring 130 having the rectangular sectional shape,as illustrated in FIG. 12B, an outer-diameter side ridge line section ischamfered. In this way, by adopting the snap ring having the rectangularsectional shape in which the outer-diameter side ridge line section ischamfered or the snap ring having a circular sectional shape, it ispossible to smoothly reduce the diameter of the snap ring 130 so thatthe snap ring 130 is easily set into the annular groove 129 of the outermember 25 when the outer member 25 is press-fitted in the hole of theknuckle 34. Note that, although being formed as a flat surface, an outerdiameter surface 130 b of the snap ring 130 illustrated in FIG. 12 maybe formed as a protruding curved surface.

At the time of this press fitting, the snap ring 130 engaged with theannular groove 129 of the outer peripheral surface of the outer member25 is guided to the inner diameter surface 34 a of the knuckle 34.Consequently, the snap ring 130 is reduced in diameter and is allowed toslide to the annular groove 128 of the inner diameter surface 34 a ofthe knuckle 34. Then, the diameter reducing force is canceled in a statein which the snap ring 130 corresponds to the annular groove 128 of theinner diameter surface 34 a of the knuckle 34, and the snap ring 130 isexpanded in diameter (returns to the free state) and engaged with thisannular groove 128. Specifically, when the snap ring 130 is insertedinto the inner diameter surface 34 a of the knuckle 34 in a state ofbeing mounted to the outer peripheral surface of the outer member 25 andreduced in diameter by elastic deformation, and then moved in the axialdirection, the snap ring 130 is expanded in diameter by elasticity andexpanded in the inner diameter surface 34 a of the knuckle 34 as soon asarriving at the position of the annular groove 128 of the inner diametersurface 34 a of the knuckle 34. In this way, the snap ring 130 isengaged with both the snap ring grooves 128 and 129.

Further, the chamfered section 90 is provided on the outboard-side edgeof the inner diameter surface 34 a of the knuckle 34. Thus, insertionwork of the axle module into the inner diameter surface 34 a of theknuckle 34 can be more easily performed. In particular, the snap ring130 mounted to the outer member 25 is smoothly and gradually reduced indiameter while being guided by the chamfered section 90, and thussmoothly slides on the inner diameter surface 34 a of the knuckle 34.

It is preferred that, as a material of the snap ring 130, a materialsmaller in shearing stress than materials of the outer member 25 and theknuckle 34 be adopted. There are various materials of the knuckle 34,which generally include cast iron, an aluminum alloy die-casting, and analuminum alloy mold. Further, although varying in accordance withmaterials, shapes, a thickness, and the like, allowed shearing stress ina case of an aluminum alloy die-casting is equal to or lower than 200MPa as a rough indication.

Meanwhile, yield stress of about 5.7 kN (580 kgf) is required in a caseof a vehicle of 1500 cc class. With the yield stress of 5.7 kN, the snapring is not deformed or broken even when thrust load of 5.7 kN isapplied to the snap ring. Although depending on a dimension of the snapring 130, shearing stress in this case is about 10 MPa (5 to 15 MPa).Thus, it is preferred that the material of the snap ring 130 haveshearing stress in a range of from 5 MPa to 150 MPa.

Examples of such a material include a thermoplastic synthetic resin.Specific examples thereof include polypropylene, an acrylic resin, andan acrylonitrile-butadiene-styrene resin (ABS resin). Snap rings made ofa resin can be mass-produced by injection molding at relatively lowcost. Therefore, at the time of disassembly, the outer member 25 can bedrawn out by being applied with a drawing force exceeding shearingstress of the snap ring 130. At this time, the snap ring 130 is deformedor broken and allows disassembly, and thus breakage of the outer member25 and the knuckle 34 is prevented. At the time of re-assembly, the snapring deformed or broken is replaced with new one.

In the embodiment, the hub wheel 1 is not provided with a pilot section,and thus exhibits a shape to which cold forging can be easily performed,which contributes to improvement of productivity. In this case, a memberwhich is other than the hub wheel 1 and has a pilot section may bemounted to the hub wheel 1. FIG. 14 illustrates an example of the casewhere a brake rotor 142 is used as such a member. Specifically, a pilotsection 144 is provided to the brake rotor 142, and an outer peripheralsurface 21 a of the flange 21 of the hub wheel 1 is used as a brakepilot. In this case, the shape of the hub wheel 1 is simplified becausethe wheel pilot section is not provided, and forging is easilyperformed. Thus, the hub wheel 1 can be manufactured by the cold forgingat low cost.

As a matter of course, the pilot section can be provided to the hubwheel as in the conventional example having been already described inrelation to FIG. 45. For example, as illustrated in FIG. 15, a pilotsection 146 formed of a brake pilot 148 a and a wheel pilot 148 b may beprovided to an outboard-side end surface of the flange 21 of the hubwheel 1.

Next, description is made of the effects of the illustrated embodiment.

In the wheel bearing device, because the entire fitting contact regions38 of the projections 35 and the recesses 36 in the recess-projectionfitting structure M are held in close contact with each other, a gap inwhich a backlash occurs is not formed in the radial direction and thecircumferential direction. Therefore, the entire fitting regionscontribute to rotation torque transmission, stable torque transmissionis possible, and abnormal noise is not caused.

The wheel bearing device is excellent in productivity because it isunnecessary to form spline sections and the like in a member (in thiscase, hub wheel 1) in which the recesses 36 are formed. Further, becausephase alignment of the splines is unnecessary, it is possible to notonly realize improvement of assemblability, prevent damage to the toothsurfaces during press fitting, but also maintain a stable fit state.

In addition, because compressive residual stress is applied to theprojections 35, improvement of the wear resistance of the projections 35is realized. Specifically, by applying compressive residual stress,residual austenite can be transformed into martensite, and thus the wearresistance can be improved. Therefore, even when driving torque acts andslightly relative displacement supposedly occurs in therecess-projection fitting structure M, it is possible to suppressoccurrence of fretting wear, to thereby prevent abrasive wear in therecess-projection fitting structure. Consequently, a torque transmittingfunction can be stably exerted without backlash over a long period oftime.

The compressive-residual-stress application means may include shotpeening, and compressive residual stress can be stably increased by thepeening. In addition, general-purpose shot peening can be used, and thuscost reduction can be realized.

When the hardness of the projections 35 ranges from 50 HRC to 65 HRC,hardness sufficient for being press-fitted in the opposite side can beprovided, and thus press-fitting properties can be improved. When thehardness on the opposite side ranges from 10 HRC to 30 HRC,press-fitting can be performed.

The projections 35 can be hardened by heat hardening treatment, that is,by high-frequency heat treatment. Thus, the following advantages of thehigh-frequency heat treatment can be realized (local heating can beperformed and hardening conditions can be easily adjusted; oxidation isreduced because heating can be performed in a short period of time;hardening distortion is reduced in comparison with other methods;surface hardness is high and excellent wear resistance can be obtained;selection of the depth of the hardened layer is relatively easy; andautomation is easily realized and assembly into a machine process linecan be realized). In particular, high compressive residual stress can beapplied by combining the shot peening with the high-frequency heattreatment, and thus improvement of fatigue strength can be expected.

When a diameter difference between the outer diameter dimension of theshaft section 12 and the inner diameter dimension of the hole 22 of thehub wheel 1 is represented as Δd, the height of the projection isrepresented as h, and a ratio of the diameter difference and the heightis represented as Δd/2 h, a relation among the diameter difference, theheight, and the ratio is set to be 0.3<Δd/2 h<0.86. Therefore, it ispossible to sufficiently secure a press-fitting margin of theprojections 35. In other words, when Δd/2 h is equal to or smaller than0.3, torsion strength falls. Further, if Δd/2 h exceeds 0.86, the entireprojections 35 bite in the opposite side because of very smalldecentering and press-fitting tilt during press fitting, moldability ofthe recess-projection fitting structure M is deteriorated, andpress-fitting load suddenly increases. When moldability of therecess-projection fitting structure M is deteriorated, because not onlytorsion strength falls but also an expansion amount of the hub wheelouter diameter increases, there are problems in that, for example, thefunction of the bearing 2 inserted in the hub wheel 1 is affected androtation life is reduced. In contrast, by setting Δd/2 h to 0.3 to 0.86,moldability of the recess-projection fitting structure M is stabilized,fluctuation in press-fitting load is eliminated, and stable torsionstrength can be obtained.

Because the tapered section 22 d can form a guide at the start of pressfitting, it is possible to press-fit the shaft section 12 of the jointouter race 5 into the hole 22 of the hub wheel 1 without causingdecentering and perform stable torque transmission. Further, because theouter diameter D4 of the short cylindrical section 66 is set to besmaller than the inner diameter dimension D of the fitting hole 22 a ofthe hole 22, the short cylindrical section 66 exerts an aligning work.Therefore, it is possible to press-fit the shaft section into the hubwheel while preventing decentering and perform more stable pressfitting.

Generation of hoop stress on the bearing raceway surface is suppressedby arranging the recess-projection fitting structure M while avoiding aposition right below the raceway surface of the roller bearing 2.Consequently, it is possible to prevent occurrence of a deficiency ofthe bearing such as a reduction in rolling fatigue life, occurrence of acrack, and stress corrosion crack. Thus, high quality bearing can beprovided.

The shaft section 12 of the joint outer race 5 can be effectivelyprevented from slipping off from the hole 22 of the hub wheel 1 (inparticular, slipping off in the axial direction to the shaft side) bythe shaft section slip-off preventing structure M1. Consequently, it ispossible to maintain a stable connection state and realize improvementof a quality of the wheel bearing device. Further, because the shaftsection slip-off preventing structure M1 is the end expanded-diametercaulking section 65, screw fastening in the past can be omitted.Therefore, it is unnecessary to form a screw section projecting to theshaft section 12 from the hole 22 of the hub wheel 1. Thus, it ispossible to realize a reduction in weight, omit screw fastening work,and improve assembly workability. Moreover, in the end expanded-diametercaulking section 65, because a part of the shaft section 12 of the jointouter race 5 only has to be expanded, it is possible to easily performformation of the shaft section slip-off preventing structure M1. Notethat, in the movement of the shaft section 12 of the joint outer race 5in the reverse joint direction, pressing force in a direction forfurther press-fitting the shaft section 12 is necessary. Therefore,positional shift in the reverse joint direction of the shaft section 12of the outer race 5 extremely hardly occurs. Even if the shaft section12 shifts in this direction, because the bottom of the mouth section 11of the joint outer race 5 is abutted to the caulking section 31 of thehub wheel 1, the shaft section 12 of the outer race 5 does not slip offfrom the hub wheel 1.

The hardness of the axial end portions of the projections of the shaftsection 12 of the joint outer race 5 of the constant-velocity universaljoint T1 is set to be higher than that of the inner diameter surface ofthe hole of the hub wheel 1, and the shaft section 12 is press-fitted inthe hole 22 of the hub wheel 1 from the axial end portion side of theprojections 35. Thus, recess formation with respect to the hole of theinner diameter surface of the hub wheel 1 is easily performed. Further,it is possible to set the hardness on the shaft section side to be high,to thereby improve torsion strength of the shaft section 12. Note that,the projections 35 can be formed by a spline normally formed in theshaft of this kind. In this case, it is easy to form the projections 35at low cost.

Further, because the end portion of the hub wheel 1 is caulked andabutted to the inner race 24 of the roller bearing 2, bearing preload isapplied. Thus, it is unnecessary to abut the mouth section 11 of thejoint outer race 5 to the inner race 24 for the purpose of applyingbearing preload. Therefore, it is possible to press-fit the shaftsection 12 of the joint outer race 5 without taking into account contactwith the inner race 24 and realize improvement of connectability(assemblability) of the hub wheel 1 and the joint outer race 5. Becausethe mouth section 11 is in a non-contact state with respect to the hubwheel 1, it is possible to prevent occurrence of abnormal noise owing tocontact between the mouth section 11 and the hub wheel 1.

Further, when the recesses 36 are formed by press-fitting the shaftsection 12 into the hub wheel 1, work hardening occurs on the recesses36 side. The work hardening means that, when plastic deformation(plastic working) is applied to an object, resistance againstdeformation increases as a degree of deformation increases and theobject becomes harder than a material not subjected to deformation.Therefore, in accordance with plastic deformation during press fitting,the inner diameter surface 37 of the hub wheel 1 on the recesses 36 sidehardens. It is possible to realize improvement of rotation torquetransmission performance.

The inner diameter side of the hub wheel 1 is relatively soft.Therefore, it is possible to realize improvement of fittability(adhesiveness) in fitting the projections 35 of the outer diametersurface of the shaft section 12 of the joint outer race 5 in therecesses 36 of the hole inner diameter surface of the hub wheel 1. It isfurther possible to accurately suppress a backlash from occurring in theradial direction and the circumferential direction.

Because the foreign-matter intrusion preventing means W is provided, itis possible to prevent intrusion of foreign matters into therecess-projection fitting structure M. That is, intrusion of rainwaterand foreign matters is prevented by the foreign-matter intrusionpreventing means W, and it is possible to prevent deterioration inadhesiveness owing to intrusion of rainwater and foreign matters intothe recess-projection fitting structure M.

When the seal member 99 is arranged between the end portion of the hubwheel 1 and the bottom of the mouth section 11, the gap 98 between theend portion of the hub wheel 1 and the bottom of the mouth section 11 isclosed by the seal member 99. Thus, rainwater and foreign matters areprevented from intruding from the gap 98 into the recess-projectionfitting structure M. The seal member 99 only has to be capable of beinginterposed between the end portion of the hub wheel 1 and the bottom ofthe mouth section 11. Thus, for example, an existing (commerciallyavailable) O-ring and the like can be used, and hence foreign-matterintrusion preventing means can be configured at low cost. In addition,the commercially available O-ring and the like vary in material andsize, and thus it is possible to configure, without additionallyproducing a special components, foreign-matter intrusion preventingmeans which surely exerts a sealing function.

The end expanded-diameter caulking section (tapered locking piece 65)that engages with the inner diameter surface of the hub wheel 1 (in thiscase, the inner diameter surface of the tapered hole 22 b) throughintermediation of the seal material (seal member configuring theforeign-matter intrusion preventing means W2) is provided further on theoutboard side than the recess-projection fitting structure M. Therefore,it is possible to prevent intrusion of foreign matters from a sidefurther on the outboard side than the recess-projection fittingstructure M. That is, it is possible to avoid intrusion of foreignmatters from the outboard side.

In this way, when the foreign-matter intrusion preventing means W1 andW2 are provided further on the inboard side than the recess-projectionfitting structure M and further on the outboard side than therecess-projection fitting structure M, intrusion of foreign matters fromboth end sides in the axial direction of the recess-projection fittingstructure M is prevented. Therefore, it is possible to stably preventdeterioration in adhesiveness over a long period of time.

By providing a pocket section 100 for storing an extruded portion 45caused by recess formation by the press fitting, it is possible to hold(maintain) the extruded portion 45 in this pocket section 100. Theextruded portion 45 does not enter the inside of the vehicle and thelike on the outside of the device. In other words, it is possible tokeep the extruded portion 45 stored in the pocket section 100, it isunnecessary to perform removal processing for the extruded portion 45,and it is possible to realize a reduction in assembly work man-hour andrealize improvement of assembly workability and cost reduction.

When a hardness difference between the projections 35 (projections onthe shaft section 12 side) and the opposite side (inner diameter surfaceof the hub wheel 1) is less than 20 HRC, as shown in the graph of FIG.8, press-fitting load is increased and there is a risk of a damagedstate in which so-called “tears” are generated during press fitting andthe like. Thus, in this embodiment, specifically, the hardness of thehardened layer H is set to about 50 HRC to 65 HRC and the hardness ofthe unhardened section is set to about 10 HRC to 30 HRC, that is, thehardness difference therebetween is set to 20 points or more in HRC.With this setting, press fitting can be performed at relatively lowload, and in addition, tears are not generated on the projections 35.

FIG. 16 illustrates a second embodiment. The shaft section slip-offpreventing structure M1 of the wheel bearing device is configured byproviding a tapered locking piece 70 that projects to the outer diameterdirection in a part of the shaft section 12 rather than forming theshort cylindrical section 66 illustrated in FIG. 5 in advance.

In this case, a jig 71 illustrated in FIG. 17 is used. The jig 71includes a columnar main body section 72 and a short cylindrical section73 connected to a distal end of the main body section 72. Asmall-diameter step section 74 is provided at a distal end of an outerperipheral surface of the short cylindrical section 73. Therefore, adistal end wedge section 75 is formed in the jig 71. As illustrated inFIG. 18, if the distal end wedge section 75 is driven (load in the arrowa direction is applied) to an end surface 12 c of the shaft section 12,a sectional shape of the distal end wedge section 75 on the outerdiameter side is a tilting surface, and the outer diameter side of theend of the shaft section 12 is expanded in diameter by thesmall-diameter step section 74 forming the tilting surface.

Consequently, at least a part of the tapered locking piece 70 comes intopress-contact or contact with the inner diameter surface of the taperedhole 22 b. Therefore, like the tapered locking piece 65 illustrated inFIG. 1 and the like, such a tapered locking piece 70 can effectivelyprevent the shaft section 12 of the outer race 5 from slipping off inthe axial direction from the hole 22 of the hub wheel 1. Consequently,it is possible to maintain a stable connected state and realizeimprovement of a quality of the wheel bearing device. Note that, aninner diameter surface of the distal end wedge section 75 may be formedin a tapered shape.

FIG. 19 illustrates a third embodiment. The shaft section slip-offpreventing structure M1 of the wheel bearing device is configured by anouter collar-like locking piece 76 formed by caulking a part of theshaft section 12 to project in the outer diameter direction. In thiscase, in the hole 22 of the hub wheel 1, the stepped surface 22 e isprovided between the fitting hole 22 a and the tapered hole 22 b. Theouter collar-like locking piece 76 locks to the stepped surface 22 e.

In the shaft section slip-off preventing structure M1, a jig 67illustrated in FIG. 20 is used. The jig 67 includes a cylindrical member78. An outer diameter D5 of the cylindrical member 78 is set to belarger than an outer diameter D7 of the end of the shaft section 12 andan inner diameter D6 of the cylindrical member 78 is set to be smallerthan the outer diameter D7 of the end of the shaft section 12.

Therefore, if axes of the jig 67 and the shaft section 12 of the outerrace 5 are aligned and load is applied in the arrow a direction to theend surface 12 c of the shaft section 12 by an end surface 67 a of thejig 67 in this state in which the axes are aligned, as illustrated inFIG. 21, an outer peripheral side of the end surface 12 c of the shaftsection 12 is crushed and the outer collar-like locking piece 76 can beformed.

Because the above-mentioned outer collar-like locking piece 76 lockswith the stepped surface 22 e, like the tapered locking piece 65illustrated in FIG. 1 and the like, the outer collar-like locking piece76 can effectively prevent the shaft section 12 of the outer race 5 fromslipping off in the axial direction from the hole 22 of the hub wheel 1.Consequently, it is possible to maintain a stable connected state andrealize improvement of a quality of the wheel bearing device.

If the jig 67 illustrated in FIG. 20 is used, as illustrated in FIG.22A, the outer collar-like locking piece 76 is formed along acircumferential direction. Therefore, if pressing sections are disposedat a predetermined pitch (e.g., 90° pitch) along the circumferentialdirection as a jig, as illustrated in FIG. 22B, a plurality of outercollar-like locking pieces 76 are disposed at the predetermined pitchalong the circumferential direction. Even if the plurality of outercollar-like locking pieces 76 are arranged at the predetermined pitchalong the circumferential direction as illustrated in FIG. 22B, becausethe outer collar-like locking pieces 76 lock to the stepped surface 22e, it is possible to effectively prevent the shaft section 12 of theouter race 5 from slipping off in the axial direction from the hole 22of the hub wheel 1.

As the shaft section slip-off preventing structure M1, bolt and nutcoupling may be used as illustrated in FIG. 23 of a fourth embodiment, asnap ring may be used as illustrated in FIG. 24 of a fifth embodiment,or coupling means such as welding may be used as illustrated in FIG. 25of a sixth embodiment.

In FIG. 23, a screw shaft section 80 is connected to the shaft section12 and a nut member 81 is screwed on the screw shaft section 80. The nutmember 81 is brought into contact with the stepped surface 22 e of thehole 22. Consequently, the shaft section 12 is regulated from slippingoff from the hole 22 of the hub wheel 1 to the shaft side.

In FIG. 24, a shaft extending section 83 is provided further on theoutboard side than the spline 41. A circumferential groove 84 isprovided in the shaft extending section 83 and a snap ring 85 is fittedin the circumferential groove 84. In the hole 22 of the hub wheel 1 ofthe shaft section 12, a step section 22 f to which the snap ring 85locks is provided between the fitting hole 22 a and the tapered hole 22b. Consequently, the snap ring 85 locks to the step section 22 f toregulate the shaft section 12 from slipping off from the hole 22 of thehub wheel 1 to the shaft side.

In FIG. 25, an end outer peripheral surface of the shaft section 12 andan opening edge on the stepped surface 22 e side of the fitting hole 22a are joined by welding. Consequently, the shaft section 12 is regulatedfrom slipping off from the hole 22 of the hub wheel 1 to the shaft side.In this case, a welding region We may be disposed over the entirecircumference or may be disposed at a predetermined pitch along thecircumferential direction.

In the wheel bearing device according to the present invention, asillustrated in FIG. 26 illustrating a seventh embodiment, the shaftsection slip-off preventing structure M1 does not have to be provided.In this case, as illustrated in FIG. 27, in the circumferential groove101, a side surface 101 a on the spline 41 side is a plane orthogonal tothe axial direction and a side surface 101 b on an opposite spline sideis a tapered surface that is expanded in diameter from a groove bottom101 c to the opposite spline side. A disc-like collar section 102 forcentering is provided further on the opposite spline side than the sidesurface 101 b of the circumferential groove 101. An outer diameterdimension D4 a of the collar section 102 is set to be the same as orslightly smaller than the hole diameter of the fitting hole 22 a of thehole 22. In this case, a very small gap t is provided between an outerdiameter surface 102 a of the collar section 102 and the inner diametersurface of the fitting hole 22 a of the hole 22.

By providing, in the axial direction of the pocket section 100, thecollar section 102 for centering with the hole 22 of the hub wheel 1 onthe opposite projection side, ejection of the extruded portion 45 in thepocket section 100 to the collar section 102 side is eliminated.Therefore, the extruded portion 45 is more stably stored. Moreover,because the collar section 102 is used for centering, it is possible topress-fit the shaft section 12 into the hub wheel 1 while preventingdecentering. Therefore, it is possible to highly accurately connect theouter race 5 and the hub wheel 1 and to perform stable torquetransmission.

Because the collar section 102 is used for centering during pressfitting, it is preferred to set an outer diameter dimension thereof to adegree slightly smaller than a hole diameter of the fitting hole 22 a ofthe hole 22 of the hub wheel 1. That is, if the outer diameter dimensionof the collar section 102 is the same as or larger than the holediameter of the fitting hole 22 a, the collar section 102 itself ispress-fitted into the fitting hole 22 a. When the collar section 102 ispress-fitted into the fitting hole 22 a, if the collar section 102 andthe fitting hole 22 a are decentered, the projections 35 of therecess-projection fitting structure M are press-fitted in this state andthe shaft section 12 and the hub wheel 1 are connected under a state inwhich the axis of the shaft section 12 and the axis of the hub wheel 1are not aligned. Further, if the outer diameter dimension of the collarsection 102 is much smaller than the hole diameter of the fitting hole22 a, the collar section 102 does not function as a section forcentering. Therefore, it is preferred to set the very small gap tbetween the outer diameter surface 102 a of the collar section 102 andthe inner diameter surface of the fitting hole 22 a of the hole 22 toabout 0.01 mm to 0.2 mm.

Note that, as illustrated in FIGS. 26 and 27, when the shaft sectionslip-off preventing structure M1 is not provided, the collar section 102as the section for centering of the shaft section 12 may be omitted.

Next, FIG. 28 illustrates a case where the recess-projection fittingstructure M allows separation by application of a drawing force in theaxial direction. Thus, the hub wheel 1 and the shaft section 12 of theouter race 5 of the constant-velocity universal joint 3 are connected toeach other through intermediation of a bolt member 54.

The hole 22 of the hub wheel 1 in this case has the shaft sectionfitting hole 22 a and the tapered hole 22 b on the outboard side. Apositioning inner wall 22 g projecting in an inner diameter direction isprovided between the shaft section fitting hole 22 a and the taperedhole 22 b. Further, the hole 22 has the large diameter section 22 c onan opening side further on an opposite positioning inner wall side thanthe shaft section fitting hole 22 a and a small diameter section 48further on a positioning inner wall side than the shaft section fittinghole 22 a. The tapered section (tapered hole) 22 d is provided betweenthe large diameter section 22 c and the shaft section fitting hole 22 a.This tapered section 22 d is reduced in diameter along a press-fittingdirection in coupling the hub wheel 1 and the shaft section 12 of theouter race 5. Note that, a recessed dent section 51 is provided on anend surface on an opposite shaft section fitting hole side of thispositioning inner wall 22 c.

Further, a screw hole 50 opening to the end surface on the outboard sideis provided in an axis section of the shaft section 12. An opening ofthe screw hole 50 is formed as a tapered section 50 a expanded toward anopening side. Further, a small diameter section 12 b is provided at theend on the outboard side of the shaft section 12. In other words, theshaft section 12 includes a main body section 12 a having a largediameter and the small diameter section 12 b.

A bolt member 54 is screwed in the screw hole 50 of the shaft section 12from the outboard side. The bolt member 54 includes, as illustrated inFIG. 29, a flanged head 54 a and a screw shaft 54 b. The screw shaft 54b has a large diameter base section 55 a, a small diameter main bodysection 55 b, and a screw section 55 c on a distal end side. In thiscase, a through hole 56 is provided in the positioning inner wall 22 g,the shaft 54 b of the bolt member 54 is inserted through this throughhole 56, and the screw section 55 c is screwed in the screw hole 50 ofthe shaft section 12. A hole diameter d1 of the through hole 56 is setto be slightly larger than the outer diameter d2 of the large diameterbase section 55 a of the shaft 54 b. Specifically, the hole diameter d1is set such that a difference between the hole diameter d1 and the outerdiameter d2 is about 0.05 mm<d1−d2<0.5 mm. Note that, a maximum outerdiameter of the screw section 55 c is set to be the same as or slightlysmaller than the outer diameter of the large diameter base section 55 a.

In the wheel bearing device, as illustrated in FIG. 30, a shaft sectionpress-fitting guide structure M2 for performing guide for press fittingof the shaft section 12 during press fitting is provided on a projectionpress-fitting start side. In this case, the shaft section press-fittingguide structure M2 includes a female spline 44 provided in the taperedsection 22 d of the hole 22. That is, as illustrated in FIG. 31A,guiding recesses 44 a are provided at a predetermined pitch (in thiscase, a pitch same as the arrangement pitch for the projections 35)along the circumferential direction on the shaft section fitting hole 22a side of the tapered section 22 d.

In this case, as illustrated in FIG. 33, a bottom diameter dimension D15of the guiding recesses 44 a is set to be larger than the maximum outerdiameter of the projections 35, i.e., the outer diameter dimension(circumscribed circle diameter) D1 of the circle connecting the vertexesof the projections 35 as the projections 41 a of the spline 41. Asillustrated in FIG. 31A, radial gaps C1 are formed between the vertexesof the projections 35 and the bottoms of the guiding recesses 44 a.

Also in this wheel bearing device, the shaft section 12 of the outerrace 5 of the constant-velocity universal joint 3 is press-fitted intothe hub wheel 1 when the hub wheel 1 and the constant-velocity universaljoint 3 are connected to each other. This press fitting is effected, asillustrated in FIG. 32, until the end surface 52 of the small diametersection 12 b of the shaft section 12 comes into contact with an endsurface 53 of the positioning inner wall 22 g.

After press fitting, the bolt member 54 is screwed in the screw hole 50of the shaft section 12 from the outboard side. By screwing the boltmember 54 in the screw hole 50 of the shaft section 12 in this way, aflange section 95 of the head 54 a of the bolt member 54 is brought intocontact with the recessed dent section 51 of the positioning inner wall22 g. Consequently, the positioning inner wall 22 g is nipped by the endsurface 52 on the outboard side of the shaft section 12 and the head 54a of the bolt member 54.

In this case, a seal material (not shown) may be interposed also betweena bearing surface 95 a of the bolt member 54 and the positioning innerwall 22 g. For example, a seal material (seal agent) made of variouskinds of resins that are hardened after application and capable ofexerting sealing performance between the bearing surface 95 a and thebottom surface of the recessed dent section 51 of the positioning innerwall 22 g only has to be applied to the bearing surface 95 a of the boltmember 54. Note that, as this seal material, a material that is notdeteriorated in an atmosphere in which this wheel bearing device is usedis selected.

By bolt fixation, slip-off of the shaft section 12 from the hub wheel 1in the axial direction is regulated, and torque can be stablytransmitted over a long period of time. In particular, with provision ofthe positioning inner wall 22 g nipped by the end surface 52 on theoutboard side of the shaft section 12 of the outer race 5 and the head54 a of the bolt member 54, the bolt fixation is stabilized anddimension accuracy of the wheel bearing device is stabilized due to thepositioning. In addition, it is possible to secure a stable length as anaxial length of the recess-projection fitting structure M disposed alongthe axial direction and to realize improvement of torque transmissionperformance.

Further, because the seal material is interposed between the bearingsurface 95 a of the bolt member 54 for performing the bolt fixation ofthe hub wheel 1 and the shaft section 12 of the outer race 5, and thepositioning inner wall 22 g, it is possible to prevent intrusion ofrainwater, foreign matters, and the like into the recess-projectionfitting structure M from the bolt member 54, and to realize improvementof quality. Because the shaft section press-fitting guide structure M2is provided, the shaft section 12 can be press-fitted along the shaftsection press-fitting guide structure M2 when being press-fit to thehole 22 of the hub wheel 1.

When the shaft section 12 is press-fitted in the hole 22 of the hubwheel 1, the extruded portion 45 formed in accordance therewith isstored, while being curled, into a pocket section (storing section) 57provided on an outer diameter side of the small diameter section 12 b ofthe shaft section 12.

Other configuration details of this axle module illustrated in FIG. 28are the same as those of the axle module illustrated in FIG. 1.Therefore, the components same as those illustrated in FIG. 1 aredenoted by the same reference symbols and description of the componentsis omitted. Thus, after the axle module is assembled as illustrated inFIG. 34, the following steps are performed: this axle module is let intothe knuckle 34 from the inboard-side constant-velocity universal jointT2 side; the axle module is then caused to pass the outboard-sideconstant-velocity universal joint T1; and lastly, the outer member 25 ofthe wheel bearing device is press-fitted into the inner peripheralsurface 34 a of the hole of the knuckle 34 as illustrated in FIG. 35.Therefore, the axle module illustrated in FIG. 28 also realizesoperations and effects same as those of the axle module illustrated inFIG. 1.

In the wheel bearing device, if the bolt member 54 is removed byscrewing back the bolt member 54 from the state illustrated in FIG. 29,the hub wheel 1 can be drawn out from the outer race 5. In other words,a fitting force of the recess-projection fitting structure M is largeenough that the outer race 5 can be drawn out by applying a drawingforce equal to or larger than a predetermined force to the outer race 5.

For example, the hub wheel 1 and the constant-velocity universal joint 3can be separated by a jig 103 illustrated in FIG. 36. The jig 103includes a base 104, a pressing bolt member 106 screwed in a screw hole105 of the base 104 to be capable of being screwed in and back, and ascrew shaft 109 screwed in the screw hole 50 of the shaft section 12. Athrough hole 107 is provided in the base 104. The bolt 33 of the hubwheel 1 is inserted through the through hole 107 and a nut member 108 isscrewed on the bolt 33. When the nut member 108 is screwed on the bolt33, the base 104 and the flange 21 of the hub wheel 1 are superimposedand the base 104 is attached to the hub wheel 1.

In this way, after the base 104 has been mounted to the hub wheel 1, orbefore mounting the base 104, the screw shaft 109 is screwed in thescrew hole 50 of the shaft section 12 so that a base section 109 a mayprotrude to the outboard side from the positioning inner wall 22 g. Theprotruding amount of the base section 109 a is set to be larger than theaxial length of the recess-projection fitting structure M. The screwshaft 109 and the pressing bolt member 106 are arranged in the same axis(on the axis of the wheel bearing device).

After that, as illustrated in FIG. 36, the pressing bolt member 106 isscrewed in the screw hole 105 of the base 104 from the outboard side,and in this state, the bolt member 106 is caused to threadedly advanceto the screw shaft 109 side in the direction of the arrow. In thisprocess, the screw shaft 109 and the pressing bolt member 106 arearranged in the same axis (on the axis of the wheel bearing device).Therefore, with the threading advancement, the pressing bolt member 106presses the screw shaft 109 in an arrow direction. This causes the outerrace 5 to move in the arrow direction with respect to the hub wheel 1,and the hub wheel 1 is removed from the outer race 5.

Further, under the state in which the outer race 5 is removed from thehub wheel 1, it is possible to connect the hub wheel 1 and the outerrace 5 together again using, for example, the bolt member 54. That is,as a state in which the base 104 is removed from the hub wheel 1 and thescrew shaft 109 is removed from the shaft section 12, the projections 35of the shaft section 12 are inserted into the guiding recesses 44 a asillustrated in FIG. 38A. Consequently, phases of the male spline 41 onthe shaft section 12 side and the female spline 42 of the hub wheel 1formed by the previous press-fitting are aligned. When the phases arealigned, as illustrated in FIG. 31A, the radial gaps C1 are formedbetween the vertexes of the projections 35 and the bottoms of theguiding recesses 44 a.

In this state, as illustrated in FIG. 37, the bolt member 54 is screwedin the screw hole 50 of the shaft section 12 through intermediation ofthe through hole 56, and the bolt member 54 is caused to threadedlyadvance with respect to the screw hole 50. As a result, as illustratedin FIG. 38B, the shaft section 12 is gradually fitted into the hub wheel1. At this time, the hole 22 is slightly expanded in diameter and allowsentry in the axial direction of the shaft section 12. The shaft section12 enters until the end surface 52 of the small diameter section 12 b ofthe shaft section 12 comes into contact with the end surface 53 of thepositioning inner wall 22 g. In this case, the positioning inner wall 22g and the small diameter section 12 b come into contact with each other,and at the same time, as illustrated in FIG. 38C, the end surfaces 35 aof the projections 35 come into contact with end surfaces 36 a of therecesses 36. When the movement in the axial direction is stopped, thehole 22 is reduced in diameter to return to the original diameter.Consequently, as in the previous press fitting, it is possible to surelyconfigure the recess-projection fitting structure M in which the entirerecess fitting regions of the projections 35 are held in close contactwith the recesses 36 corresponding thereto.

Note that, the opening of the screw hole 50 of the shaft section 12 isformed as the tapered section 50 a opening toward the opening side.Therefore, there is an advantage that the screw shaft 109 and the boltmember 54 are easily screwed in the screw hole 50.

In the first time (press fitting for molding the recesses 36 in theinner diameter surface 37 of the hole 22), because press-fitting load isrelatively large, for press fitting, it is necessary to use a pressmachine or the like. Meanwhile, in press fitting in the second time,because press-fitting load is smaller than the press-fitting load in thefirst time. Therefore, it is possible to stably and accurately press-fitthe shaft section 12 into the hole 22 of the hub wheel 1 without usingthe press machine or the like. Therefore, it is possible to separate andconnect the outer race 5 and the hub wheel 1 on the site.

By applying the drawing force in the axial direction to the shaftsection 12 of the outer race 5 in this way, the outer race 5 can beremoved from the hole 22 of the hub wheel 1. Therefore, it is possibleto realize improvement of workability for repairing and inspection(maintainability) of each component. Moreover, by press-fitting theshaft section 12 of the outer race 5 into the hole 22 of the hub wheel 1again after the repairing and inspection of each of the components, therecess-projection fitting structure M in which the entire fittingcontact regions 38 of the projections 35 and the recesses 36 are held inclose contact with each other can be configured. Therefore, it ispossible to configure again a wheel bearing device capable of performingstable torque transmission.

The shaft section press-fitting guide structure M2 has the guidingrecesses 44 a for aligning a phase of the one-side projections 35 and aphase of the other-side recesses 36. Therefore, when the shaft section12 of the outer joint member is press-fitted into the hole 22 of the hubwheel 1 again, the shaft section 12 fits in the recesses 36 formed bythe previous press fitting and does not damage the recesses 36.Therefore, it is possible to highly accurately configure again therecess-projection fitting structure M in which a gap that causes abacklash is not formed in the radial direction and the circumferentialdirection.

By forming gaps between the vertexes of the projections 35 and thebottoms of the guiding recesses 44 a, the projections 35 can be easilyfitted in the guiding recesses 44 a in a pre-press fitting process.Moreover, the guiding recesses 44 a do not hinder press-fitting of theprojections 35. Therefore, it is possible to realize improvement ofassemblability.

When the bolt member 54 is caused to threadedly advance with respect tothe screw hole 50, as illustrated in FIG. 33, the base section 55 a ofthe bolt member 54 corresponds to the through hole 56. In addition, thehole diameter d1 of the through hole 56 is set to be slightly largerthan the outer diameter d2 of the large diameter base section 55 a ofthe shaft 54 b (specifically, set to about 0.05 mm<d1−d2<0.5 mm). Thus,a guide when the bolt member 54 threadedly advances in the screw hole 50can be configured by the outer diameter of the base section 55 a of thebolt member 54 and the inner diameter of the through hole 56. Withoutdecentering, the shaft section 12 can be press-fitted in the hole 22.Note that, when the axial length of the through hole 56 is extremelyshort, the through hole 56 cannot function as a stable guide.Conversely, when the axial length of the through hole 56 is extremelylong, the thickness dimension of the positioning inner wall 22 g becomeslarge, and thus the axial length of the recess-projection fittingstructure M cannot be secured, and the weight of the hub wheel 1 becomeslarge. Therefore, it is possible to make various changes taking intoaccount those disadvantages.

In the embodiment, as illustrated in FIG. 31A, the radial gaps C1 areformed between the vertexes of the projections 35 and the bottoms of theguiding recesses 44 a. However, as illustrated in FIG. 31B,circumferential gaps C2 and C2 may be formed between the sides of theprojections 35 and the sides of the guiding recesses 44 a. Further, asillustrated in FIG. 31C, the radial gaps C1 may be formed between thevertexes of the projections 35 and the bottoms of the guiding recesses44 a and the circumferential gaps C2 may be formed between the sides ofthe projections 35 and the sides of the guiding recesses 44 a. Byforming such gaps, it is possible to easily fit the projections 35 inthe guiding recesses 44 a in the pre-press fitting process. Moreover,the guiding recesses 44 a do not hinder press fitting of the projections35.

The shaft section press-fitting guide structure M2 may be thatillustrated in FIGS. 39. In FIG. 39A, the end on the recess-projectionfitting structure M side of each of the guiding recesses 44 a is atilting surface 77 b that is reduced in diameter along a press-fittingdirection (press-fitting progress direction). In other words, a tiltangle θ of the tilting surface 77 b is, for example, about 30° to 60°.

In FIGS. 39B and 39C, a radial depth dimension of each of the guidingrecesses 44 a is reduced in diameter along the press-fitting direction.Further, in FIG. 39B, the end on the recess-projection fitting structureM side is a flat surface 77 a orthogonal to the press-fitting direction.In FIG. 39C, the end on the recess-projection fitting structure M sideis the tilting surface 77 b that is reduced in diameter along thepress-fitting direction (press-fitting progress direction).

If the end on the recess-projection fitting structure M side of each ofthe guiding recesses 44 a is the flat surface 77 a orthogonal to thepress-fitting direction, when the shaft section 12 is press-fitted intothe hole 22, the flat surface 77 a can receive the shaft section 12.Further, if the end is the tilting surface 77 b, the projections 35 canbe stably fitted in the recesses 36 on the opposite side from theguiding recesses 44 a. Even if the radial depth of each of the guidingrecesses 44 a is reduced in diameter along the press-fitting direction,the projections 35 can be stably fitted in the recesses 36 on theopposite side from the guiding recesses 44 a.

Next, FIG. 40 illustrates another embodiment. In this case, a pilotsection 148 formed of the brake pilot section 148 a and the wheel pilotsection 148 b is provided to the outboard-side end surface of the hubwheel 1. Other configuration details of this axle module illustrated inFIG. 40 are the same as those of the axle module illustrated in FIG. 1.Therefore, the components same as those illustrated in FIG. 1 aredenoted by the same reference symbols and description of the componentsis omitted.

Thus, after the axle module is assembled as illustrated in FIG. 41, thefollowing steps are performed: this axle module is let into the knuckle34 from the inboard-side constant-velocity universal joint T2 side; thencaused to pass the outboard-side constant-velocity universal joint T1;and lastly, the outer member 25 of the wheel bearing device ispress-fitted into the inner peripheral surface 34 a of the hole of theknuckle 34 as illustrated in FIG. 42. Therefore, the axle moduleillustrated in FIG. 40 also realizes operations and effects same asthose of the axle module illustrated in FIG. 1.

In the spline 41 illustrated in FIG. 3, the pitch of the projections 41a and the pitch of the recesses 41 b are set to the same value. Thus, inthe above-mentioned embodiment, as illustrated in FIG. 3B, acircumferential thickness L of projecting direction intermediate regionsof the projections 35, and a circumferential dimension L0 in a positioncorresponding to the intermediate region between the projections 35adjacent to each other in the circumferential direction aresubstantially the same.

Meanwhile, as illustrated in a first modified example of therecess-projection fitting structure M of FIG. 43A, a circumferentialthickness L2 of the projecting direction intermediate regions of theprojections 35 may be smaller than a circumferential dimension L1 in aposition corresponding to the intermediate region between theprojections 35 adjacent to each other in the circumferential direction.In other words, in the spline 41 formed in the shaft section 12, thecircumferential thickness (tooth thickness) L2 of the projectingdirection intermediate regions of the projections 35 is set to besmaller than the circumferential thickness (tooth thickness) L1 ofprojecting direction intermediate regions of projections 43 on the hubwheel 1 side that fit in among the projections 35.

Therefore, a sum Σ(B1+B2+B3+ . . . ) of tooth thicknesses of theprojections 35 in the entire circumference on the shaft section 12 sideis set to be smaller than a sum Σ(A1+A2+A3+ . . . ) of tooth thicknessesof the projections 43 (projecting teeth) on the hub wheel 1 side.Consequently, it is possible to increase a shearing area of theprojections 43 on the hub wheel 1 side and secure torsion strength.Moreover, because the tooth thickness of each of the projections 35 issmall, it is possible to reduce press-fitting load and realizeimprovement of press-fitting performance. When a sum of circumferentialthicknesses of the projections 35 is set to be smaller than a sum ofcircumferential thicknesses of the projections 43 on the opposite side,it is unnecessary to set the circumferential thickness L2 of all theprojections 35 smaller than the dimension L1 in the circumferentialdirection between the projections 35 adjacent to each other in thecircumferential direction. In other words, even if the circumferentialthickness of arbitrary projections 35 among the plurality of projections35 is the same as or larger than a dimension in the circumferentialdirection between the projections adjacent to each other in thecircumferential direction, a sum of circumferential thicknesses only hasto be smaller than a sum of dimensions in the circumferential direction.

Note that, the projections 35 in FIG. 43A are trapezoidal incross-section. However, a shape of the projections 35 may be an involutetooth shape as illustrated in a second modified example of FIG. 43B.

In each embodiment described above, the spline 41 forming theprojections 35 is formed on the shaft section 12 side. Hardeningtreatment is applied to the spline 41 of the shaft section 12 and theinner diameter surface of the hub wheel 1 is not hardened (rowmaterial). Meanwhile, as illustrated in a third modified example of therecess-projection fitting structure M of FIG. 44A and FIG. 44B, a spline111 (including projected streaks 111 a and recessed streaks 111 b)subjected to hardening treatment may be formed on the inner diametersurface of the hole 22 of the hub wheel 1. Hardening treatment may notbe applied to the shaft section 12. Note that, the spline 111 can alsobe formed by various machining methods such as broaching, cutting,pressing, and drawing, which are publicly known and used means. Further,as heat hardening treatment, various kinds of heat treatment such asinduction hardening, and carburizing and quenching can be adopted.

Also in this case, it is preferred that compressive residual stress beapplied with respect to the projections 35 of the hub wheel 1 bycompressive-residual-stress application means such as shot peening.

In this case, the projecting direction intermediate regions of theprojections 35 correspond to positions of the recess forming surfacebefore recess formation (outer diameter surface of the shaft section12). In other words, a diameter dimension (minimum diameter dimension ofthe projections 35) D8 of a circle connecting the vertexes of theprojections 35 as the projections 111 a of the spline 111 is set to besmaller than an outer diameter dimension D10 of the shaft section 12. Adiameter dimension (inner diameter dimension of fitting hole innerdiameter surfaces among the projections) D9 of a circle connectingbottoms of the recesses 111 b of the spline 111 is set to be larger thanthe outer diameter dimension D10 of the shaft section 12. In otherwords, a relation among the diameter dimensions and the outer diameterdimension is D8<D10<D9. Also in this case, when a diameter differencebetween the outer diameter dimension D10 of the shaft section 12 and theinner diameter dimension D9 of the hole 22 of the hub wheel 1 isrepresented as Δd, the height of the projections 35 is represented as h,and a ratio of the diameter difference and the height is represented asΔd/2 h, a relation among the diameter difference, the height, and theratio is 0.3<Δd/2 h<0.86.

If the shaft section 12 is press-fitted into the hole 22 of the hubwheel 1, the recesses 36 in which the projections 35 on the hub wheel 1side are fitted can be formed on the outer peripheral surface of theshaft section 12 by the projections 35. Consequently, the entire fittingcontact regions 38 of the projections 35 and the recesses that fit inthe projections 35 are brought into close contact with each other.

The fitting contact regions 38 are ranges B illustrated in FIG. 44B andranges from halfway sections to the tops of the ridges in cross-sectionof the projections 35. Further, a gap 112 is formed further on an outerdiameter side than the outer peripheral surface of the shaft section 12between the projections 35 adjacent to each other in the circumferentialdirection.

In this way, even when the projections 35 of the recess-projectionfitting structure M are provided on the inner diameter surface of thehole 22 of the hub wheel 1 and press-fitting is performed, compressiveresidual stress is applied to those projections 35 by thecompressive-residual-stress application means, and the operations andeffects same as those in the above-mentioned embodiments are realized.In particular, because it is unnecessary to perform hardening treatment(heat treatment) on the shaft section side, there is an advantage inthat the outer race 5 of the constant-velocity universal joint isexcellent in productivity.

In the wheel bearing device illustrated in FIG. 44A and FIG. 44B, as inthe bearing device described above, it is preferred to provide the shaftsection press-fitting guide structure M2. In this case, the guidingrecesses 44 a only have to be provided on the shaft section 12 side.Further, the radial gaps C1 can be formed between the vertexes of theprojections 35 and the bottoms of the guiding recesses 44 a, thecircumferential gaps C2 and C2 can be formed between the sides of theprojections 35 and the sides of the guiding recesses 44 a, or the radialgaps C1 and the circumferential gaps C2 and C2 can be formed.

In the case illustrated in FIG. 44A and FIG. 44B, as in the casedescribed above, the extruded portion 45 is formed by press fitting.Therefore, it is preferred to provide the pocket section 100 that storesthe extruded portion 45. Because the extruded portion 45 is formed onthe mouth side of the shaft section 12, the pocket section 100 isprovided on the hub wheel 1 side.

In this way, in the wheel bearing device in which the projections 35 ofthe recess-projection fitting structure M are provided on the innerdiameter surface 37 of the hole 22 of the hub wheel 1, the hardness ofthe axial end portions of the projections 35 is set to be higher thanthat of the outer diameter section of the shaft section 12 of the outerrace 5, and the shaft section 12 is press-fitted as described above, itis unnecessary to perform hardness treatment (heat treatment) on theshaft section side. Therefore, the wheel bearing device is excellent inproductivity of the outer joint member (outer race 5) of theconstant-velocity universal joint.

The embodiments of the present invention have been described. However,the present invention is not limited to the embodiments and variousmodifications of the embodiments are possible. For example, the shape ofthe projections 35 of the recess-projection fitting structure M istriangular in cross-section according to the embodiment illustrated inFIG. 3 and is trapezoidal in cross-section according to the embodimentillustrated in FIG. 43A. Besides, projections of various shapes such asa semicircular shape, a semi-elliptical shape, and a rectangular shapecan be adopted. An area, the number, and a circumferential directiondisposing pitch, and the like of the projections 35 can also bearbitrarily changed. In other words, it is unnecessary to form thespline 41 or 61 and form the projections (projecting teeth) 41 a or 111a of the spline 41 or 111 as the projections 35 of the recess-projectionfitting structure M. The projections 35 may be something like keys ormay form wavy fitting surfaces of a curved line shape. In short, it issufficient that the projections 35 disposed along the axial directionare press-fitted into the opposite side, the recesses 36 coming in closecontact with and fitting in the projections 35 can be formed on theopposite side by the projections 35, the entire fitting contact regions38 of the projections 35 and the recesses that fit in the projections 35are brought into close contact with each other, and rotation torque canbe transmitted between the hub wheel 1 and the constant-velocityuniversal joint 3.

The hole 22 of the hub wheel 1 may be a deformed-shape hole such as apolygonal hole other than a circular hole. A cross-sectional shape ofthe end of the shaft section 12 fitted and inserted into the hole 22 maybe a deformed-shape cross-section such as a polygon other than acircular cross-section. Further, when the shaft section 12 ispress-fitted into the hub wheel 1, only press-fitting start-ends of theprojections 35 have hardness higher than that of the regions where therecesses 36 are formed. Therefore, it is unnecessary to set the hardnessof the entire projections 35 high. In FIG. 3 and the like, the gap 40 isformed. However, the projections 35 may bite in the inner diametersurface 37 of the hub wheel 1 up to the recesses among the projections35. Note that, as a hardness difference between the projections 35 sideand the side of the recess formation surface formed by the projections35, it is preferred to set the hardness difference to be equal to orlarger than 20 points in HRC. As long as the projections 35 can bepress-fitted, the hardness difference may be smaller than 20 points.

The end surfaces (press-fitting start-ends) of the projections 35 arethe surfaces orthogonal to the axial direction in the embodiments.However, the end surfaces may be surfaces tilting at a predeterminedangle with respect to the axial direction. In this case, the endsurfaces may tilt to the opposite projection side from the innerdiameter side to the outer diameter side or may tilt to the projectionside.

Further, it is also possible to provide small recesses arranged at apredetermined circumferential pitch in the inner diameter surface 37 ofthe hole 22 of the hub wheel 1. It is necessary for the small recessesto have a volume smaller than that of the recesses 36. By thus providingthe small recesses, it is possible to improve the press-fitting propertyof the projections 35. That is, by thus providing the small recesses, itis possible to reduce the capacity of the extruded portion 45 formedduring press fitting of the projections 35, and hence it is possible toreduce the press-fitting resistance. Further, because the extrudedportion 45 can be made smaller, it is possible to reduce the volume ofthe pocket section 100, making it possible to improve the processabilityof the pocket section 100 and the strength of the shaft section 12. Notethat, the small recesses may be of various shapes such as asemi-elliptical or a rectangular shape, and the number of small recesscan also be set arbitrarily.

While welding is adopted as the coupling means illustrated in FIG. 25,it is also possible to adopt adhesive instead of welding. Further, it isalso possible to use rollers as the rolling elements 30 of the bearing2. Further, while in the above-mentioned embodiments the thirdgeneration wheel bearing device is described, it is also possible toadopt the first, second, and fourth generation wheel bearing device.Note that, when press fitting the projections 35, it is possible to movethe member on which the projections 35 are formed, with the member inwhich the recesses 36 are formed being stationary. Conversely, it isalso possible to move the member in which the recesses 36 are formed,with the member on which the projections 35 are formed being stationary.Further, it is also possible to move both of them. Note that, in theconstant-velocity universal joint 3, the inner race 6 and the shaft 10may be integrated with each other through intermediation of therecess-projection fitting structure M as described with reference to theabove-mentioned embodiments. Note that, when being used in the shaftsection slip-off preventing structure M1, the snap ring 85 asillustrated in FIG. 24 can be provided on the base section side (mouthside) of the shaft section 12.

The seal material interposed between the bearing surface 95 a of thebolt member 54, which fixes by a bolt the hub wheel 1 and the shaftsection 12, and the positioning inner wall 22 g is formed by applyingthe resin to the bearing surface 95 a side of the bolt member 54 in theembodiments. However, conversely, the resin may be applied to thepositioning inner wall 22 g side. Alternatively, the resin may beapplied to the bearing surface 95 a side and the positioning inner wall22 g side. Note that, when the bolt member 54 is screwed in, if thebearing surface 95 a of the bolt member 54 and the bottom surface of therecessed dent section 51 of the positioning inner wall 22 g areexcellent in adhesiveness, such a seal material can also be omitted. Inother words, it is possible to improve adhesiveness of the bolt member54 with the bearing surface 95 a by grinding the bottom surface of therecessed dent section 51. It goes without saying that, even if thebottom surface of the recessed dent section 51 is not ground and is in aso-called turning finish state, the seal material can be omitted as longas adhesiveness can be exerted.

As the guiding recesses 44 a, as illustrated in FIGS. 31A, 31B, and 31C,the gaps C1 and C2 are formed among the projections 35. A dimension ofthose gaps only has to be a dimension that does not cause decenteringand shaft misalignment during press fitting and prevents the projections35 from coming into press-contact with the inner surfaces of the guidingrecesses 44 a to cause an increase in press-fitting load. Further, theaxial length of the guiding recesses 44 a can be arbitrarily set. If theguiding recesses 44 a are long in the axial direction, it is preferredin alignment. However, an upper limit of the axial length is limitedbecause of the axial length of the hole 22 of the hub wheel 1.Conversely, if the axial length of the hole 22 of the hub wheel 1 issmall, the guiding recesses 44 a do not function as a guide anddecentering and shaft misalignment are likely to occur. Therefore, it isnecessary to determine the axial length of the guiding recesses 44 ataking into account those points.

Incidentally, a sectional shape of the guiding recesses 44 a is notlimited to that illustrated in FIG. 31 and the like as long as theprojections 35 can be inserted in the guiding recesses 44 a. Thesectional shape can be variously changed according to a sectional shapeand the like of the projections 35. The number of guiding recesses 44 adoes not have to be the same as the number of projections 35 and may besmaller or larger than the number of projections 35. In short, severalprojections 35 only have to be inserted in several guiding recesses 44 aand a phase of the projections 35 and a phase of the recesses 36 formedin the previous press fitting only have to coincide with each other.

The tilt angle θ of the tilting surfaces 77 b of the ends of the guidingrecesses 44 a and the tilt angle θ2 of the bottoms of the guidingrecesses 44 a can also be arbitrarily changed. Further, if the tiltangle θ of the tilting surfaces 77 b is close to 90°, the tiltingsurfaces 77 b are functionally the same as the flat surfaces 77 aorthogonal to the press-fitting direction. If the tilt angle θ is small,the guiding recesses 44 a are long and the axial length of therecess-projection fitting structure M is small. If the tilt angle θ2 ofthe bottoms is large, it is difficult to form the guiding recesses 44 a.Conversely, if the tilt angle θ2 is small, the function of the tiltedguiding recesses 44 a cannot be exerted. Therefore, it is necessary toset the tilt angles θ and θ2 taking into account those points.

In the above-mentioned embodiments, although the back surface 11 a ofthe mouth section 11 of the outer race 5 and an end surface 31 a of thecaulking section 31 are not held in contact with each other, thosesurfaces may be brought into contact with each other. When the backsurface 11 a of the mouth section 11 of the outer race 5 and the endsurface 31 a of the caulking section 31 are held in contact with eachother, there is a risk that abrasion between contact surfaces causesabnormal noise. However, even in a contact state, setting for preventingabnormal noise can be made depending on a contact force, materials ofthe contact surfaces, and finished states of the contact surfaces. Thus,those surfaces are held in contact with each other in the presentinvention.

Specifically, when the caulking section 31 of the hub wheel 1 and theback surface 11 a of the mouth section 11 are brought into contact witheach other and the contact surface pressure therebetween exceeds 100MPa, abnormal noise is likely to be caused. When torque load is large, adifference occurs in torsion amounts of the outer race 5 of theconstant-velocity universal joint 3 and the hub wheel 1. Sudden slipoccurs in the contact section of the outer race 5 of theconstant-velocity universal joint 3 and the hub wheel 1 because of thisdifference and abnormal noise occurs. Meanwhile, when the contactsurface pressure is equal to or lower than 100 MPa, it is possible toprevent sudden slip from occurring and suppress occurrence of abnormalnoise. Consequently, it is possible to configure a silent wheel bearingdevice. The surface pressure of the contact section of the end surface31 a of the caulking section 31 of the hub wheel 1 and the back surface11 a of the mouth section 11 is influenced by the magnitude of fasteningtorque of the bolt member 54. However, an axial force generated by thefastening torque is consumed as a frictional force in the axialdirection of the recess-projection fitting section or a force foradditionally molding the recess-projection fitting section(press-fitting load at the time of molding the recess-projection fittingsection), and thus the contact surface pressure becomes higher only whena higher axial force is applied. Accordingly, the contact surfacepressure can be easily suppressed to 100 MPa or lower, and thusstick-slip noise is not generated. Note that, even when being 100 MPa orlower, the contact surface pressure needs to beset to surface pressureor higher, with which a seal structure can be configured.

A sectional shape of the snap ring 130 is not limited to thatillustrated in FIGS. 10 and 11, and it is possible to adopt snap ringshaving various shapes such as an elliptic or oblong shape, a triangularshape, or polygonal shapes each having more sides and corners than apentagonal shape has. The compressive-residual-stress application meansis not limited to the shot peening, and it is possible to adopt othermeans such as laser peening or ultrasonic impact treatment.

Note that, only in the embodiment illustrated in FIG. 5, the hardenedlayers H and H1 are indicated by cross hatching illustrated on the hubwheel 1 and the outer race 5 of the constant-velocity universal joint 3.However, such hardened layers are formed also in the other embodiments.

INDUSTRIAL APPLICABILITY

The present invention can be applied to wheel bearing device of thefirst generation having the structure in which double row rollerbearings are independently used, the second generation in which avehicle body attachment flange is integrally provided in an outermember, the third generation in which an inner raceway surface on oneside of the double row roller bearings is integrally formed with anouter periphery of a hub wheel integrally having a wheel attachmentflange, and the fourth generation in which a constant-velocity universaljoint is integrated with the hub wheel and an inner raceway surface ofthe other side of the double row roller bearings is integrally formedwith an outer periphery of an outer joint member configuring theconstant-velocity universal joint.

REFERENCE SIGNS LIST

-   -   1 hub wheel    -   2 bearing    -   3 constant-velocity universal joint    -   10 shaft    -   11 mouth section    -   12 shaft section (stem section)    -   21 wheel attachment flange    -   22 hole    -   22 g positioning inner wall    -   25 outer member    -   26 outer raceway surface    -   27 outer raceway surface    -   28 inner raceway surface    -   29 inner raceway surface    -   30 rolling element    -   34 knuckle    -   35 projection    -   36 recess    -   38 fitting contact region    -   39 inner member    -   65 end expanded-diameter caulking section (tapered locking        piece)    -   128 annular groove    -   129 annular groove    -   130 snap ring    -   M recess-projection fitting structure    -   M1 shaft section slip-off preventing structure    -   M2 shaft section press-fitting guide structure    -   T1 outboard side of constant-velocity universal joint    -   T2 inboard side of constant-velocity universal joint

1. A wheel bearing device, comprising a wheel bearing comprising: anouter member having double-row outer raceway surfaces formed on an innerperiphery of the outer member; an inner member having double-row innerraceway surfaces formed on an outer periphery of the inner member; androlling elements arranged between the double-row outer raceway surfacesof the outer member and the double-row inner raceway surfaces of theinner member, the inner member comprising a hub wheel having a wheelattachment flange protrudingly provided on an outer diameter surface ofthe hub wheel, the hub wheel and a shaft section of an outer jointmember of a constant-velocity universal joint being coupled to eachother through intermediation of a recess-projection fitting structure,the shaft section being fitted and inserted in a hole of the hub wheel,wherein: the recess-projection fitting structure is configured byproviding projections extending in an axial direction on any one of anouter diameter surface of the shaft section of the outer joint memberand an inner diameter surface of the hole of the hub wheel,press-fitting the projections in another of the outer diameter surfaceand the inner diameter surface along the axial direction, and formingrecesses brought into close contact and fitted with respect to theprojections by this press fitting in the another of the outer diametersurface and the inner diameter surface, the projections and the recessesbeing held in close contact with each other through intermediation ofentire fitting contact regions; and the outer member is separable in thefollowing configuration from a knuckle only by deformation or breakageof a snap ring caused by application of a drawing force larger than adrawing force acting in normal use, the configuration being obtained byfitting the outer member in a hole of the knuckle of a vehicle with apredetermined fit, forming annular grooves respectively in an outerperipheral surface of the outer member and an inner peripheral surfaceof the hole of the knuckle, and preventing the outer member fromslipping off from the knuckle by the snap ring engaged with both theannular grooves.
 2. A wheel bearing device according to claim 1, whereinshearing stress of a material of the snap ring is smaller than shearingstress of a material of the knuckle.
 3. A wheel bearing device accordingto claim 2, wherein the shearing stress of the snap ring falls within arange of from 5 to 150 MPa.
 4. A wheel bearing device according to claim1, wherein the material of the snap ring is a thermoplastic syntheticresin.
 5. A wheel bearing device according to claim 1, wherein anouter-diameter side ridge line section of the snap ring is chamfered. 6.A wheel bearing device according to claim 1, wherein the snap ring has acircular sectional shape.
 7. A wheel bearing device according to claim1, wherein an outboard-side edge of the hole of the knuckle ischamfered.
 8. A wheel bearing device according to claim 1, wherein: theouter member is fitted in the hole of the knuckle by press fitting; andat a time of this press fitting, after being reduced in diameter bybeing guided to the inner peripheral surface of the hole of the knuckleand then allowed to slide to the annular groove of the hole of theknuckle, the snap ring engaged with the annular groove in the outerperipheral surface of the outer member is engaged with the annulargroove of the hole of the knuckle by being expanded in diameter in astate of corresponding to the annular groove of the hole of the knuckle.9. A wheel bearing device, comprising a wheel bearing comprising: anouter member having double-row outer raceway surfaces formed on an innerperiphery of the outer member; an inner member having double-row innerraceway surfaces formed on an outer periphery of the inner member; androlling elements arranged between the double-row outer raceway surfacesof the outer member and the double-row inner raceway surfaces of theinner member, the inner member comprising a hub wheel having a wheelattachment flange protrudingly provided on an outer diameter surface ofthe hub wheel, the hub wheel and a shaft section of an outer jointmember of a constant-velocity universal joint being separably coupled toeach other through intermediation of a recess-projection fittingstructure, the shaft section being fitted and inserted in a hole of thehub wheel, wherein: the recess-projection fitting structure isconfigured by providing projections extending in an axial direction onany one of an outer diameter surface of the shaft section of the outerjoint member and an inner diameter surface of the hole of the hub wheel,press-fitting the projections in another of the outer diameter surfaceand the inner diameter surface along the axial direction, and formingrecesses brought into close contact and fitted with respect to theprojections by this press fitting in the another of the outer diametersurface and the inner diameter surface, the projections and the recessesbeing held in close contact with each other through intermediation ofentire fitting contact regions; and compressive residual stress isapplied to the projections by compressive-residual-stress applicationmeans.
 10. A wheel bearing device according to claim 9, wherein thecompressive-residual-stress application means comprises shot peening.11. A wheel bearing device according to claim 1, wherein the projectionsof the recess-projection fitting structure are provided on the shaftsection of the outer joint member.
 12. A wheel bearing device accordingto claim 11, wherein at least hardness of axial end portions of theprojections is set to be higher than hardness of an inner diametersection of the hole of the hub wheel.
 13. A wheel bearing deviceaccording to claim 1, wherein the projections of the recess-projectionfitting structure are provided on the inner diameter surface of the holeof the hub wheel.
 14. A wheel bearing device according to claim 13,wherein at least the hardness of the axial end portions of theprojections is set to be higher than hardness of an outer diametersection of the shaft section of the outer joint member of theconstant-velocity universal joint.
 15. A wheel bearing device accordingto claim 11, wherein the hardness of the axial end portions of theprojections is of from 50 HRC to 65 HRC.
 16. A wheel bearing deviceaccording to claim 11, wherein hardness of a side formed by pressfitting is of from 10 HRC to 30 HRC.
 17. A wheel bearing deviceaccording to claim 11, wherein at least the axial end portions of theprojections are hardened by heat hardening treatment, that is, byhigh-frequency heat treatment.
 18. A wheel bearing device according toclaim 1, wherein a circumferential thickness of a projecting directionintermediate region of each of the projections is set to be smaller thana circumferential dimension at a position corresponding to theprojecting direction intermediate region between the projectionsadjacent to each other in a circumferential direction.
 19. A wheelbearing device according to claim 1, wherein a sum of circumferentialthicknesses of projecting direction intermediate regions of theprojections is set to be smaller than a sum of circumferentialthicknesses at positions corresponding to the projecting directionintermediate regions in projections on an opposite side that fit inamong the projections adjacent to one another in the circumferentialdirection.
 20. A wheel bearing device according to claim 1, wherein therecess-projection fitting structure allows separation by the applicationof the drawing force in the axial direction.
 21. A wheel bearing deviceaccording to claim 1, wherein the inner diameter surface of the hubwheel is provided with a wall section with which a distal end portion ofthe shaft section of the outer joint member of the constant-velocityuniversal joint comes into contact so that positioning of the shaftsection in the axial direction is performed.
 22. A wheel bearing deviceaccording to claim 1, wherein a shaft section slip-off preventingstructure for regulating slip-off of the shaft section from the hubwheel is provided between the shaft section of the outer joint member ofthe constant-velocity universal joint and the inner diameter surface ofthe hub wheel.
 23. A wheel bearing device according to claim 22, whereinthe shaft section slip-off preventing structure is constituted by an endexpanded-diameter caulking section of the shaft section of the outerjoint member, the end expanded-diameter caulking section being engagedwith the inner diameter surface of the hub wheel and being unsubjectedto hardening treatment.
 24. An axle module, comprising: an outboard-sideconstant-velocity universal joint; an inboard-side constant-velocityuniversal joint; and a shaft connected to the outboard-sideconstant-velocity universal joint on one end side of the shaft andconnected to the inboard-side constant-velocity universal joint onanother end side of the shaft, wherein the constant-velocity universaljoint of the wheel bearing device according to claim 1 is used as theoutboard-side constant-velocity universal joint.
 25. An axle moduleaccording to claim 24, wherein a maximum outer diameter of each of theoutboard-side constant-velocity universal joint and the inboard-sideconstant-velocity universal joint is set to be smaller than an outerdiameter of the outer member of the wheel bearing of the wheel bearingdevice.
 26. A wheel bearing device according to claim 9, wherein theprojections of the recess-projection fitting structure are provided onthe shaft section of the outer joint member.
 27. A wheel bearing deviceaccording to claim 9, wherein the projections of the recess-projectionfitting structure are provided on the inner diameter surface of the holeof the hub wheel.
 28. A wheel bearing device according to claim 9,wherein a circumferential thickness of a projecting directionintermediate region of each of the projections is set to be smaller thana circumferential dimension at a position corresponding to theprojecting direction intermediate region between the projectionsadjacent to each other in a circumferential direction.
 29. A wheelbearing device according to claim 9, wherein a sum of circumferentialthicknesses of projecting direction intermediate regions of theprojections is set to be smaller than a sum of circumferentialthicknesses at positions corresponding to the projecting directionintermediate regions in projections on an opposite side that fit inamong the projections adjacent to one another in the circumferentialdirection.
 30. A wheel bearing device according to claim 9, wherein therecess-projection fitting structure allows separation by the applicationof the drawing force in the axial direction.
 31. A wheel bearing deviceaccording to claim 9, wherein the inner diameter surface of the hubwheel is provided with a wall section with which a distal end portion ofthe shaft section of the outer joint member of the constant-velocityuniversal joint comes into contact so that positioning of the shaftsection in the axial direction is performed.
 32. A wheel bearing deviceaccording to claim 9, wherein a shaft section slip-off preventingstructure for regulating slip-off of the shaft section from the hubwheel is provided between the shaft section of the outer joint member ofthe constant-velocity universal joint and the inner diameter surface ofthe hub wheel.
 33. An axle module, comprising: an outboard-sideconstant-velocity universal joint; an inboard-side constant-velocityuniversal joint; and a shaft connected to the outboard-sideconstant-velocity universal joint on one end side of the shaft andconnected to the inboard-side constant-velocity universal joint onanother end side of the shaft, wherein the constant-velocity universaljoint of the wheel bearing device according to claim 9 is used as theoutboard-side constant-velocity universal joint.